File: System\Xml\XPathNodePointer.cs
Web Access
Project: src\src\libraries\System.Data.Common\src\System.Data.Common.csproj (System.Data.Common)
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Data;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Xml.XPath;
 
#pragma warning disable 618 // ignore obsolete warning about XmlDataDocument
 
namespace System.Xml
{
    internal sealed class XPathNodePointer : IXmlDataVirtualNode
    {
        private readonly WeakReference _owner;  // Owner of this pointer (an DataDocumentXPathNavigator). When the associated DataDocumentXPathNavigator (the owner) goes away, this XPathNodePointer can go away as well.
        private readonly XmlDataDocument _doc;
        private XmlNode _node;
        private DataColumn? _column;
        private bool _fOnValue;
        internal XmlBoundElement? _parentOfNS;
        internal const string StrReservedXmlns = "http://www.w3.org/2000/xmlns/";
        internal const string StrReservedXml = "http://www.w3.org/XML/1998/namespace";
        internal const string StrXmlNS = "xmlns";
        private bool _bNeedFoliate;
 
        internal static ReadOnlySpan<int> XmlNodeTypeToXpathNodeTypeMap =>
        [
            /*XmlNodeType.None*/ -1,
            /*XmlNodeType.Element*/ (int)XPathNodeType.Element,
            /*XmlNodeType.Attribute*/ (int)XPathNodeType.Attribute,
            /*XmlNodeType.Text*/ (int)XPathNodeType.Text,
            /*XmlNodeType.CDATA*/ (int)XPathNodeType.Text,
            /*XmlNodeType.EntityReference*/ -1,
            /*XmlNodeType.Entity*/ -1,
            /*XmlNodeType.ProcessingInstruction*/ (int)XPathNodeType.ProcessingInstruction,
            /*XmlNodeType.Comment*/ (int)XPathNodeType.Comment,
            /*XmlNodeType.Document*/ (int)XPathNodeType.Root,
            /*XmlNodeType.DocumentType*/ -1,
            /*XmlNodeType.DocumentFragment*/ (int)XPathNodeType.Root,
            /*XmlNodeType.Notation*/ -1,
            /*XmlNodeType.Whitespace*/ (int)XPathNodeType.Whitespace,
            /*XmlNodeType.SignificantWhitespace*/ (int)XPathNodeType.SignificantWhitespace,
            /*XmlNodeType.EndElement*/ -1,
            /*XmlNodeType.EndEntity*/ -1,
            /*XmlNodeType.XmlDeclaration*/ -1,
        ];
 
        private XPathNodeType DecideXPNodeTypeForTextNodes(XmlNode node)
        {
            //the function can only be called on text like nodes.
            Debug.Assert(XmlDataDocument.Helpers.IsTextNode(node.NodeType));
            XPathNodeType xnt = XPathNodeType.Whitespace;
            XmlNode? n = node;
            while (n != null)
            {
                switch (n.NodeType)
                {
                    case XmlNodeType.Whitespace:
                        break;
                    case XmlNodeType.SignificantWhitespace:
                        xnt = XPathNodeType.SignificantWhitespace;
                        break;
                    case XmlNodeType.Text:
                    case XmlNodeType.CDATA:
                        return XPathNodeType.Text;
                    default:
                        return xnt;
                }
                n = _doc.SafeNextSibling(n);
            }
            return xnt;
        }
 
        private XPathNodeType ConvertNodeType(XmlNode node)
        {
            if (XmlDataDocument.Helpers.IsTextNode(node.NodeType))
                return DecideXPNodeTypeForTextNodes(node);
 
            int xnt = XmlNodeTypeToXpathNodeTypeMap[(int)(node.NodeType)];
            if (xnt == (int)XPathNodeType.Attribute)
            {
                if (node.NamespaceURI == StrReservedXmlns)
                    return XPathNodeType.Namespace;
                else
                    return XPathNodeType.Attribute;
            }
            Debug.Assert(xnt != -1);
            return (XPathNodeType)xnt;
        }
 
        private static bool IsNamespaceNode(XmlNodeType nt, string ns) => nt == XmlNodeType.Attribute && ns == StrReservedXmlns;
 
        //when the constructor is called, the node has to be a valid XPath node at the valid location ( for example, the first
        //text/WS/SWS/CData nodes of a series continuous text-like nodes.
        internal XPathNodePointer(DataDocumentXPathNavigator owner, XmlDataDocument doc, XmlNode node) :
            this(owner, doc, node, null, false, null)
        {
        }
 
        internal XPathNodePointer(DataDocumentXPathNavigator owner, XPathNodePointer pointer) :
            this(owner, pointer._doc, pointer._node, pointer._column, pointer._fOnValue, pointer._parentOfNS)
        {
        }
 
        private XPathNodePointer(DataDocumentXPathNavigator owner, XmlDataDocument doc, XmlNode node, DataColumn? c, bool bOnValue, XmlBoundElement? parentOfNS)
        {
            Debug.Assert(owner != null);
            _owner = new WeakReference(owner);
            _doc = doc;
            _node = node;
            _column = c;
            _fOnValue = bOnValue;
            _parentOfNS = parentOfNS;
 
            // Add this pointer to the document so it will be updated each time region changes it's foliation state.
            _doc.AddPointer(this);
            _bNeedFoliate = false;
            AssertValid();
        }
 
        internal XPathNodePointer Clone(DataDocumentXPathNavigator owner)
        {
            RealFoliate();
            return new XPathNodePointer(owner, this);
        }
 
        internal bool IsEmptyElement
        {
            get
            {
                AssertValid();
                if (_node != null && _column == null)
                {
                    if (_node.NodeType == XmlNodeType.Element)
                    {
                        return ((XmlElement)_node).IsEmpty;
                    }
                }
                return false;
            }
        }
 
        internal XPathNodeType NodeType
        {
            get
            {
                RealFoliate();
                AssertValid();
                if (_node == null)
                {
                    return XPathNodeType.All;
                }
                else if (_column == null)
                {
                    return ConvertNodeType(_node);
                }
                else if (_fOnValue)
                {
                    return XPathNodeType.Text;
                }
                else if (_column.ColumnMapping == MappingType.Attribute)
                {
                    if (_column.Namespace == StrReservedXmlns)
                        return XPathNodeType.Namespace;
                    else
                        return XPathNodeType.Attribute;
                }
                else
                {
                    return XPathNodeType.Element;
                }
            }
        }
 
        //LDAI: From CodeReview: Perf: We should have another array similar w/
        //  xmlNodeType_To_XpathNodeType_Map that will return String.Empty for everything but the element and
        //  attribute case.
        internal string LocalName
        {
            get
            {
                RealFoliate();
                AssertValid();
                if (_node == null)
                {
                    return string.Empty;
                }
                else if (_column == null)
                {
                    XmlNodeType nt = _node.NodeType;
                    if (IsNamespaceNode(nt, _node.NamespaceURI) && _node.LocalName == StrXmlNS)
                        return string.Empty;
                    if (nt == XmlNodeType.Element || nt == XmlNodeType.Attribute || nt == XmlNodeType.ProcessingInstruction)
                        return _node.LocalName;
                    return string.Empty;
                }
                else if (_fOnValue)
                {
                    return string.Empty;
                }
                else //when column is not null
                    return _doc.NameTable.Add(_column.EncodedColumnName);
            }
        }
 
        //note that, we've have lost the prefix in this senario ( defoliation will toss prefix away. )
        internal string Name
        {
            get
            {
                RealFoliate();
                AssertValid();
                if (_node == null)
                {
                    return string.Empty;
                }
                else if (_column == null)
                {
                    XmlNodeType nt = _node.NodeType;
                    if (IsNamespaceNode(nt, _node.NamespaceURI))
                    {
                        if (_node.LocalName == StrXmlNS)
                            return string.Empty;
                        else
                            return _node.LocalName;
                    }
                    if (nt == XmlNodeType.Element || nt == XmlNodeType.Attribute || nt == XmlNodeType.ProcessingInstruction)
                        return _node.Name;
                    return string.Empty;
                }
                else if (_fOnValue)
                {
                    return string.Empty;
                }
                else
                { //when column is not null
                    //we've lost prefix in this senario.
                    return _doc.NameTable.Add(_column.EncodedColumnName);
                }
            }
        }
 
        internal string NamespaceURI
        {
            get
            {
                RealFoliate();
                AssertValid();
                if (_node == null)
                {
                    return string.Empty;
                }
                else if (_column == null)
                {
                    XPathNodeType xnt = ConvertNodeType(_node);
                    if (xnt == XPathNodeType.Element || xnt == XPathNodeType.Root || xnt == XPathNodeType.Attribute)
                        return _node.NamespaceURI;
                    return string.Empty;
                }
                else if (_fOnValue)
                {
                    return string.Empty;
                }
                else
                {
                    //When column is not null
                    if (_column.Namespace == StrReservedXmlns)
                    {
                        //namespace nodes has empty string as namespaceURI
                        return string.Empty;
                    }
 
                    return _doc.NameTable.Add(_column.Namespace);
                }
            }
        }
 
        internal string Prefix
        {
            get
            {
                RealFoliate();
                AssertValid();
                if (_node == null)
                {
                    return string.Empty;
                }
                else if (_column == null)
                {
                    if (IsNamespaceNode(_node.NodeType, _node.NamespaceURI))
                        return string.Empty;
                    return _node.Prefix;
                }
                return string.Empty;
            }
        }
 
        internal string? Value
        {
            [RequiresUnreferencedCode(DataSet.RequiresUnreferencedCodeMessage)]
            [RequiresDynamicCode(DataSet.RequiresDynamicCodeMessage)]
            get
            {
                RealFoliate();
                AssertValid();
                if (_node == null)
                    return null;
                else if (_column == null)
                {
                    string? strRet = _node.Value;
                    if (XmlDataDocument.Helpers.IsTextNode(_node.NodeType))
                    {
                        //concatenate adjacent textlike nodes
                        XmlNode? parent = _node.ParentNode;
                        if (parent == null)
                            return strRet;
                        XmlNode? n = _doc.SafeNextSibling(_node);
                        while (n != null && XmlDataDocument.Helpers.IsTextNode(n.NodeType))
                        {
                            strRet += n.Value;
                            n = _doc.SafeNextSibling(n);
                        }
                    }
                    return strRet;
                }
                else if (_column.ColumnMapping == MappingType.Attribute || _fOnValue)
                {
                    DataRow row = Row!;
                    DataRowVersion rowVersion = (row.RowState == DataRowState.Detached) ? DataRowVersion.Proposed : DataRowVersion.Current;
                    object value = row[_column, rowVersion];
                    if (!Convert.IsDBNull(value))
                        return _column.ConvertObjectToXml(value);
                    return null;
                }
                else
                    return null;
            }
        }
 
        internal string InnerText
        {
            [RequiresUnreferencedCode(DataSet.RequiresUnreferencedCodeMessage)]
            [RequiresDynamicCode(DataSet.RequiresDynamicCodeMessage)]
            get
            {
                RealFoliate();
                AssertValid();
                if (_node == null)
                {
                    return string.Empty;
                }
                else if (_column == null)
                {
                    if (_node.NodeType == XmlNodeType.Document)
                    {
                        //document node's region should always be uncompressed
                        XmlElement? rootElem = ((XmlDocument)_node).DocumentElement;
                        if (rootElem != null)
                            return rootElem.InnerText;
                        return string.Empty;
                    }
                    else
                        return _node.InnerText;
                }
                else
                {
                    DataRow row = Row!;
                    DataRowVersion rowVersion = (row.RowState == DataRowState.Detached) ? DataRowVersion.Proposed : DataRowVersion.Current;
                    object value = row[_column, rowVersion];
                    if (!Convert.IsDBNull(value))
                        return _column.ConvertObjectToXml(value);
                    return string.Empty;
                }
            }
        }
 
        internal string BaseURI
        {
            get
            {
                RealFoliate();
                if (_node != null)
                    return _node.BaseURI;
                return string.Empty;
            }
        }
 
        internal string XmlLang
        {
            get
            {
                RealFoliate();
                XmlNode curNode = _node;
                XmlBoundElement? curBoundElem;
                object? colVal;
                while (curNode != null)
                {
                    curBoundElem = curNode as XmlBoundElement;
                    if (curBoundElem != null)
                    {
                        if (curBoundElem.ElementState == ElementState.Defoliated)
                        {
                            //if not foliated, going through the columns to get the xml:lang
                            DataRow row = curBoundElem.Row!;
                            foreach (DataColumn col in row.Table.Columns)
                            {
                                if (col.Prefix == "xml" && col.EncodedColumnName == "lang")
                                {
                                    colVal = row[col];
                                    if (colVal == DBNull.Value)
                                        break; //goto its ancestor
                                    return (string)colVal;
                                }
                            }
                        }
                        else
                        {
                            //if folicated, get the attribute directly
                            if (curBoundElem.HasAttribute("xml:lang"))
                                return curBoundElem.GetAttribute("xml:lang");
                        }
                    }
                    if (curNode.NodeType == XmlNodeType.Attribute)
                        curNode = ((XmlAttribute)curNode).OwnerElement!;
                    else
                        curNode = curNode.ParentNode!;
                }
                return string.Empty;
            }
        }
 
        private XmlBoundElement? GetRowElement()
        {
            XmlBoundElement? rowElem;
            if (_column != null)
            {
                rowElem = (XmlBoundElement)_node;
                Debug.Assert(rowElem != null);
                Debug.Assert(rowElem.Row != null);
                return rowElem;
            }
 
            DataSetMapper.GetRegion(_node, out rowElem);
            return rowElem;
        }
 
        private DataRow? Row
        {
            get
            {
                XmlBoundElement? rowElem = GetRowElement();
                if (rowElem == null)
                    return null;
 
                Debug.Assert(rowElem.Row != null);
                return rowElem.Row;
            }
        }
 
        internal bool MoveTo(XPathNodePointer pointer)
        {
            AssertValid();
            if (_doc != pointer._doc)
            {
                return false;
            }
 
            _node = pointer._node;
            _column = pointer._column;
            _fOnValue = pointer._fOnValue;
            _bNeedFoliate = pointer._bNeedFoliate;
            AssertValid();
            return true;
        }
 
        private void MoveTo(XmlNode node)
        {
            // Should not move outside of this document
            Debug.Assert(node == _doc || node.OwnerDocument == _doc);
            _node = node;
            _column = null;
            _fOnValue = false;
        }
 
        private void MoveTo(XmlNode node, DataColumn? column, bool fOnValue)
        {
            // Should not move outside of this document
            Debug.Assert(node == _doc || node.OwnerDocument == _doc);
            _node = node;
            _column = column;
            _fOnValue = fOnValue;
        }
 
        private static bool IsFoliated(XmlNode node)
        {
            if (node != null && node is XmlBoundElement)
                return ((XmlBoundElement)node).IsFoliated;
            return true;
        }
 
        private int ColumnCount(DataRow row, bool fAttribute)
        {
            DataColumn? c = null;
            int count = 0;
            while ((c = NextColumn(row, c, fAttribute)) != null)
            {
                if (c.Namespace != StrReservedXmlns)
                    count++;
            }
            return count;
        }
 
        internal int AttributeCount
        {
            get
            {
                RealFoliate();
                AssertValid();
                if (_node != null)
                {
                    if (_column == null && _node.NodeType == XmlNodeType.Element)
                    {
                        if (!IsFoliated(_node))
                            return ColumnCount(Row!, true);
                        else
                        {
                            int nc = 0;
                            foreach (XmlAttribute attr in _node.Attributes!)
                            {
                                if (attr.NamespaceURI != StrReservedXmlns)
                                    nc++;
                            }
                            return nc;
                        }
                    }
                }
                return 0;
            }
        }
 
        internal DataColumn? NextColumn(DataRow row, DataColumn? col, bool fAttribute)
        {
            if (row.RowState == DataRowState.Deleted)
                return null;
 
            DataTable table = row.Table;
            DataColumnCollection columns = table.Columns;
            int iColumn = (col != null) ? col.Ordinal + 1 : 0;
            int cColumns = columns.Count;
            DataRowVersion rowVersion = (row.RowState == DataRowState.Detached) ? DataRowVersion.Proposed : DataRowVersion.Current;
 
            for (; iColumn < cColumns; iColumn++)
            {
                DataColumn c = columns[iColumn];
                if (!_doc.IsNotMapped(c) && (c.ColumnMapping == MappingType.Attribute) == fAttribute && !Convert.IsDBNull(row[c, rowVersion]))
                    return c;
            }
 
            return null;
        }
 
        internal DataColumn? PreviousColumn(DataRow row, DataColumn? col, bool fAttribute)
        {
            if (row.RowState == DataRowState.Deleted)
                return null;
 
            DataTable table = row.Table;
            DataColumnCollection columns = table.Columns;
            int iColumn = (col != null) ? col.Ordinal - 1 : columns.Count - 1;
            DataRowVersion rowVersion = (row.RowState == DataRowState.Detached) ? DataRowVersion.Proposed : DataRowVersion.Current;
 
            for (; iColumn >= 0; iColumn--)
            {
                DataColumn c = columns[iColumn];
                if (!_doc.IsNotMapped(c) && (c.ColumnMapping == MappingType.Attribute) == fAttribute && !Convert.IsDBNull(row[c, rowVersion]))
                    return c;
            }
 
            return null;
        }
 
        internal bool MoveToAttribute(string localName, string namespaceURI)
        {
            RealFoliate();
            AssertValid();
            if (namespaceURI == StrReservedXmlns)
                return false;
            if (_node != null)
            {
                //_column.ColumnMapping checkin below is not really needed since the pointer should be pointing at the node before this
                // function should even be called ( there is always a call MoveToOwnerElement() before MoveToAttribute(..)
                if ((_column == null || _column.ColumnMapping == MappingType.Attribute) && _node.NodeType == XmlNodeType.Element)
                {
                    if (!IsFoliated(_node))
                    {
                        DataColumn? c = null;
                        while ((c = NextColumn(Row!, c, true)) != null)
                        {
                            if (c.EncodedColumnName == localName && c.Namespace == namespaceURI)
                            {
                                MoveTo(_node, c, false);
                                return true;
                            }
                        }
                    }
                    else
                    {
                        Debug.Assert(_node.Attributes != null);
                        XmlNode? n = _node.Attributes.GetNamedItem(localName, namespaceURI);
                        if (n != null)
                        {
                            MoveTo(n, null, false);
                            return true;
                        }
                    }
                }
            }
            return false;
        }
 
        internal bool MoveToNextAttribute(bool bFirst)
        {
            RealFoliate();
            AssertValid();
            if (_node != null)
            {
                if (bFirst && (_column != null || _node.NodeType != XmlNodeType.Element))
                    return false;
                if (!bFirst)
                {
                    if (_column != null && _column.ColumnMapping != MappingType.Attribute)
                        return false;
                    if (_column == null && _node.NodeType != XmlNodeType.Attribute)
                        return false;
                }
                if (!IsFoliated(_node))
                {
                    DataColumn? c = _column;
                    while ((c = NextColumn(Row!, c, true)) != null)
                    {
                        if (c.Namespace != StrReservedXmlns)
                        {
                            MoveTo(_node, c, false);
                            return true;
                        }
                    }
                    return false;
                }
                else
                {
                    if (bFirst)
                    {
                        XmlAttributeCollection attrs = _node.Attributes!;
                        foreach (XmlAttribute attr in attrs)
                        {
                            if (attr.NamespaceURI != StrReservedXmlns)
                            {
                                MoveTo(attr, null, false);
                                return true;
                            }
                        }
                    }
                    else
                    {
                        XmlAttributeCollection attrs = ((XmlAttribute)_node).OwnerElement!.Attributes;
                        bool bFound = false;
                        foreach (XmlAttribute attr in attrs)
                        {
                            if (bFound && attr.NamespaceURI != StrReservedXmlns)
                            {
                                MoveTo(attr, null, false);
                                return true;
                            }
                            if (attr == _node)
                                bFound = true;
                        }
                    }
                }
            }
            return false;
        }
 
        private static bool IsValidChild(XmlNode parent, XmlNode child)
        {
            int xntChildInt = XmlNodeTypeToXpathNodeTypeMap[(int)(child.NodeType)];
            if (xntChildInt == -1)
                return false;
 
            int xntInt = XmlNodeTypeToXpathNodeTypeMap[(int)(parent.NodeType)];
            Debug.Assert(xntInt != -1);
            return xntInt switch
            {
                (int)XPathNodeType.Root =>
                    (xntChildInt == (int)XPathNodeType.Element ||
                     xntChildInt == (int)XPathNodeType.Comment ||
                     xntChildInt == (int)XPathNodeType.ProcessingInstruction),
 
                (int)XPathNodeType.Element =>
                    (xntChildInt == (int)XPathNodeType.Element ||
                     xntChildInt == (int)XPathNodeType.Text ||
                     xntChildInt == (int)XPathNodeType.Comment ||
                     xntChildInt == (int)XPathNodeType.Whitespace ||
                     xntChildInt == (int)XPathNodeType.SignificantWhitespace ||
                     xntChildInt == (int)XPathNodeType.ProcessingInstruction),
 
                _ => false,
            };
        }
 
        private static bool IsValidChild(XmlNode parent, DataColumn c)
        {
            int xntInt = XmlNodeTypeToXpathNodeTypeMap[(int)(parent.NodeType)];
            Debug.Assert(xntInt != -1);
            return xntInt switch
            {
                (int)XPathNodeType.Root => c.ColumnMapping == MappingType.Element,
                (int)XPathNodeType.Element => (c.ColumnMapping == MappingType.Element || c.ColumnMapping == MappingType.SimpleContent),
                _ => false,
            };
        }
 
        internal bool MoveToNextSibling()
        {
            RealFoliate();
            AssertValid();
            if (_node != null)
            {
                if (_column != null)
                {
                    if (_fOnValue)
                    {
                        // _fOnValue could be true only when the column is mapped as simplecontent or element
                        Debug.Assert(_column.ColumnMapping != MappingType.Attribute && _column.ColumnMapping != MappingType.Hidden);
                        return false;
                    }
                    DataRow curRow = Row!;
                    DataColumn? c = NextColumn(curRow, _column, false);
                    while (c != null)
                    {
                        if (IsValidChild(_node, c))
                        {
                            MoveTo(_node, c, _doc.IsTextOnly(c));
                            return true;
                        }
                        c = NextColumn(curRow, c, false);
                    }
                    XmlNode? n = _doc.SafeFirstChild(_node);
                    if (n != null)
                    {
                        MoveTo(n);
                        return true;
                    }
                }
                else
                {
                    XmlNode? n = _node;
                    XmlNode? parent = _node.ParentNode;
                    if (parent == null)
                        return false;
                    bool bTextLike = XmlDataDocument.Helpers.IsTextNode(_node.NodeType);
                    do
                    {
                        do
                        {
                            n = _doc.SafeNextSibling(n);
                        } while (n != null && bTextLike && XmlDataDocument.Helpers.IsTextNode(n.NodeType));
                    } while (n != null && !IsValidChild(parent, n));
                    if (n != null)
                    {
                        MoveTo(n);
                        return true;
                    }
                }
            }
            return false;
        }
 
        internal bool MoveToPreviousSibling()
        {
            RealFoliate();
            AssertValid();
            if (_node != null)
            {
                if (_column != null)
                {
                    if (_fOnValue)
                        return false;
                    DataRow curRow = Row!;
                    DataColumn? c = PreviousColumn(curRow, _column, false);
                    while (c != null)
                    {
                        if (IsValidChild(_node, c))
                        {
                            MoveTo(_node, c, _doc.IsTextOnly(c));
                            return true;
                        }
                        c = PreviousColumn(curRow, c, false);
                    }
                }
                else
                {
                    XmlNode? n = _node;
                    XmlNode? parent = _node.ParentNode;
                    if (parent == null)
                        return false;
                    bool bTextLike = XmlDataDocument.Helpers.IsTextNode(_node.NodeType);
                    do
                    {
                        do
                        {
                            n = _doc.SafePreviousSibling(n);
                        } while (n != null && bTextLike && XmlDataDocument.Helpers.IsTextNode(n.NodeType));
                    } while (n != null && !IsValidChild(parent, n));
                    if (n != null)
                    {
                        MoveTo(n);
                        return true;
                    }
                    if (!IsFoliated(parent) && (parent is XmlBoundElement))
                    {
                        DataRow? row = ((XmlBoundElement)parent).Row;
                        if (row != null)
                        {
                            DataColumn? c = PreviousColumn(row, null, false);
                            if (c != null)
                            {
                                MoveTo(parent, c, _doc.IsTextOnly(c));
                                return true;
                            }
                        }
                    }
                }
            }
            return false;
        }
 
        internal bool MoveToFirst()
        {
            RealFoliate();
            AssertValid();
            if (_node != null)
            {
                DataRow? curRow = null;
                XmlNode? parent;
                if (_column != null)
                {
                    curRow = Row;
                    parent = _node;
                }
                else
                {
                    parent = _node.ParentNode;
                    if (parent == null)
                        return false;
                    if (!IsFoliated(parent) && (parent is XmlBoundElement))
                        curRow = ((XmlBoundElement)parent).Row;
                }
                //first check with the columns in the row
                if (curRow != null)
                {
                    DataColumn? c = NextColumn(curRow, null, false);
                    while (c != null)
                    {
                        if (IsValidChild(_node, c))
                        {
                            MoveTo(_node, c, _doc.IsTextOnly(c));
                            return true;
                        }
                        c = NextColumn(curRow, c, false);
                    }
                }
                //didn't find a valid column or maybe already Foliated, go through its children nodes
                XmlNode? n = _doc.SafeFirstChild(parent);
                while (n != null)
                {
                    if (IsValidChild(parent, n))
                    {
                        MoveTo(n);
                        return true;
                    }
                    n = _doc.SafeNextSibling(n);
                }
            }
            return false;
        }
 
        internal bool HasChildren
        {
            get
            {
                RealFoliate();
                AssertValid();
                if (_node == null)
                    return false;
 
                if (_column != null)
                {
                    if (_column.ColumnMapping == MappingType.Attribute || _column.ColumnMapping == MappingType.Hidden)
                        return false;
                    return !_fOnValue;
                }
                if (!IsFoliated(_node))
                {
                    // find virtual column elements first
                    DataRow curRow = Row!;
                    DataColumn? c = NextColumn(curRow, null, false);
                    while (c != null)
                    {
                        if (IsValidChild(_node, c))
                            return true;
                        c = NextColumn(curRow, c, false);
                    }
                }
                // look for anything
                XmlNode? n = _doc.SafeFirstChild(_node);
                while (n != null)
                {
                    if (IsValidChild(_node, n))
                        return true;
                    n = _doc.SafeNextSibling(n);
                }
 
                return false;
            }
        }
 
        internal bool MoveToFirstChild()
        {
            RealFoliate();
            AssertValid();
            if (_node == null)
                return false;
 
            if (_column != null)
            {
                if (_column.ColumnMapping == MappingType.Attribute || _column.ColumnMapping == MappingType.Hidden)
                    return false;
                if (_fOnValue) //text node has no children to move to
                    return false;
                _fOnValue = true;
                return true;
            }
            if (!IsFoliated(_node))
            {
                // find virtual column elements first
                DataRow curRow = Row!;
                DataColumn? c = NextColumn(curRow, null, false);
                while (c != null)
                {
                    if (IsValidChild(_node, c))
                    {
                        MoveTo(_node, c, _doc.IsTextOnly(c));
                        return true;
                    }
                    c = NextColumn(curRow, c, false);
                }
            }
            // look for anything
            XmlNode? n = _doc.SafeFirstChild(_node);
            while (n != null)
            {
                if (IsValidChild(_node, n))
                {
                    MoveTo(n);
                    return true;
                }
                n = _doc.SafeNextSibling(n);
            }
 
            return false;
        }
 
        //this version of MoveToParent will consider Attribute type position and move to its owner element
        internal bool MoveToParent()
        {
            RealFoliate();
            AssertValid();
            if (NodeType == XPathNodeType.Namespace)
            {
                MoveTo(_parentOfNS!);
                return true;
            }
            if (_node != null)
            {
                if (_column != null)
                {
                    if (_fOnValue && !_doc.IsTextOnly(_column))
                    {
                        MoveTo(_node, _column, false);
                        return true;
                    }
                    MoveTo(_node, null, false);
                    return true;
                }
                else
                {
                    XmlNode? n;
                    if (_node.NodeType == XmlNodeType.Attribute)
                        n = ((XmlAttribute)_node).OwnerElement;
                    else
                        n = _node.ParentNode;
                    if (n != null)
                    {
                        MoveTo(n);
                        return true;
                    }
                }
            }
            return false;
        }
 
        private XmlNode? GetParent(XmlNode node)
        {
            XPathNodeType xnt = ConvertNodeType(node);
            if (xnt == XPathNodeType.Namespace)
            {
                Debug.Assert(_parentOfNS != null);
                return _parentOfNS;
            }
            if (xnt == XPathNodeType.Attribute)
                return ((XmlAttribute)node).OwnerElement;
            return node.ParentNode;
        }
 
        internal void MoveToRoot()
        {
            XmlNode node = _node;
            XmlNode? parent = _node;
            while (parent != null)
            {
                node = parent;
                parent = GetParent(parent);
            }
            _node = node;
            _column = null;
            _fOnValue = false;
            AssertValid();
        }
 
        internal bool IsSamePosition(XPathNodePointer pointer)
        {
            RealFoliate();
            pointer.RealFoliate();
            AssertValid();
            pointer.AssertValid();
            if (_column == null && pointer._column == null)
                return (pointer._node == _node && pointer._parentOfNS == _parentOfNS);
 
            return (pointer._doc == _doc
                    && pointer._node == _node
                    && pointer._column == _column
                    && pointer._fOnValue == _fOnValue
                    && pointer._parentOfNS == _parentOfNS);
        }
 
        [RequiresUnreferencedCode(DataSet.RequiresUnreferencedCodeMessage)]
        [RequiresDynamicCode(DataSet.RequiresDynamicCodeMessage)]
        private XmlNodeOrder CompareNamespacePosition(XPathNodePointer other)
        {
            XPathNodePointer xp1 = Clone((DataDocumentXPathNavigator)(_owner.Target!));
            XPathNodePointer xp2 = other.Clone((DataDocumentXPathNavigator)(other._owner.Target!));
            while (xp1.MoveToNextNamespace(XPathNamespaceScope.All))
            {
                if (xp1.IsSamePosition(xp2))
                    return XmlNodeOrder.Before;
            }
            return XmlNodeOrder.After;
        }
 
        private static XmlNode GetRoot(XmlNode node, ref int depth)
        {
            depth = 0;
            XmlNode curNode = node;
            XmlNode? parent = ((curNode.NodeType == XmlNodeType.Attribute) ? (((XmlAttribute)curNode).OwnerElement) : (curNode.ParentNode));
            for (; parent != null; depth++)
            {
                curNode = parent;
                parent = curNode.ParentNode; // no need to check for attribute since navigator can't be built on its children or navigate to its children
            }
            return curNode;
        }
 
        [RequiresUnreferencedCode(DataSet.RequiresUnreferencedCodeMessage)]
        [RequiresDynamicCode(DataSet.RequiresDynamicCodeMessage)]
        internal XmlNodeOrder ComparePosition(XPathNodePointer other)
        {
            RealFoliate();
            other.RealFoliate();
 
            if (IsSamePosition(other))
                return XmlNodeOrder.Same;
            XmlNode? curNode1, curNode2;
 
            //deal with namespace node first
            if (NodeType == XPathNodeType.Namespace && other.NodeType == XPathNodeType.Namespace)
            {
                if (_parentOfNS == other._parentOfNS)
                    return CompareNamespacePosition(other);
                //if not from the same parent
                curNode1 = _parentOfNS;
                curNode2 = other._parentOfNS;
            }
            else if (NodeType == XPathNodeType.Namespace)
            {
                Debug.Assert(other.NodeType != XPathNodeType.Namespace);
                if (_parentOfNS == other._node)
                {
                    //from the same region, NS nodes come before all other nodes
                    if (other._column == null)
                        return XmlNodeOrder.After;
                    else
                        return XmlNodeOrder.Before;
                }
                //if not from the same region
                curNode1 = _parentOfNS;
                curNode2 = other._node;
            }
            else if (other.NodeType == XPathNodeType.Namespace)
            {
                Debug.Assert(NodeType != XPathNodeType.Namespace);
                if (_node == other._parentOfNS)
                {
                    //from the same region
                    if (_column == null)
                        return XmlNodeOrder.Before;
                    else
                        return XmlNodeOrder.After;
                }
                //if not from the same region
                curNode1 = _node;
                curNode2 = other._parentOfNS;
            }
            else
            {
                if (_node == other._node)
                {
                    //compare within the same region
                    if (_column == other._column)
                    {
                        //one is the children of the other
                        Debug.Assert(_fOnValue != other._fOnValue);
                        if (_fOnValue)
                            return XmlNodeOrder.After;
                        else
                            return XmlNodeOrder.Before;
                    }
                    else
                    {
                        Debug.Assert(Row == other.Row); //in the same row
                        if (_column == null)
                            return XmlNodeOrder.Before;
                        else if (other._column == null)
                            return XmlNodeOrder.After;
                        else if (_column.Ordinal < other._column.Ordinal)
                            return XmlNodeOrder.Before;
                        else
                            return XmlNodeOrder.After;
                    }
                }
                curNode1 = _node;
                curNode2 = other._node;
            }
 
            Debug.Assert(curNode1 != null);
            Debug.Assert(curNode2 != null);
 
            if (curNode1 == null || curNode2 == null)
            {
                return XmlNodeOrder.Unknown;
            }
 
 
            int depth1 = -1, depth2 = -1;
            XmlNode root1 = XPathNodePointer.GetRoot(curNode1, ref depth1);
            XmlNode root2 = XPathNodePointer.GetRoot(curNode2, ref depth2);
            if (root1 != root2)
                return XmlNodeOrder.Unknown;
 
            if (depth1 > depth2)
            {
                while (curNode1 != null && depth1 > depth2)
                {
                    curNode1 = ((curNode1.NodeType == XmlNodeType.Attribute) ? (((XmlAttribute)curNode1).OwnerElement) : (curNode1.ParentNode));
                    depth1--;
                }
                if (curNode1 == curNode2)
                    return XmlNodeOrder.After;
            }
            else if (depth2 > depth1)
            {
                while (curNode2 != null && depth2 > depth1)
                {
                    curNode2 = ((curNode2.NodeType == XmlNodeType.Attribute) ? (((XmlAttribute)curNode2).OwnerElement) : (curNode2.ParentNode));
                    depth2--;
                }
                if (curNode1 == curNode2)
                    return XmlNodeOrder.Before;
            }
 
            XmlNode? parent1 = GetParent(curNode1!);
            XmlNode? parent2 = GetParent(curNode2!);
            XmlNode? nextNode;
            while (parent1 != null && parent2 != null)
            {
                if (parent1 == parent2)
                {
                    while (curNode1 != null)
                    {
                        nextNode = curNode1.NextSibling;
                        if (nextNode == curNode2)
                            return XmlNodeOrder.Before;
                        curNode1 = nextNode;
                    }
                    return XmlNodeOrder.After;
                }
                curNode1 = parent1;
                curNode2 = parent2;
                parent1 = curNode1.ParentNode;
                parent2 = curNode2.ParentNode;
            }
 
            Debug.Fail("Logically, we shouldn't reach here.");
            return XmlNodeOrder.Unknown;
        }
 
        internal XmlNode? Node
        {
            [RequiresUnreferencedCode(DataSet.RequiresUnreferencedCodeMessage)]
            [RequiresDynamicCode(DataSet.RequiresDynamicCodeMessage)]
            get
            {
                RealFoliate();
                AssertValid();
 
                if (_node == null)
                    return null;
 
                XmlBoundElement? rowElem = GetRowElement();
                if (rowElem != null)
                {
                    bool wasFoliationEnabled = _doc.IsFoliationEnabled;
                    _doc.IsFoliationEnabled = true;
                    _doc.Foliate(rowElem, ElementState.StrongFoliation);
                    _doc.IsFoliationEnabled = wasFoliationEnabled;
                }
                RealFoliate();
                AssertValid();
                return _node;
            }
        }
 
        bool IXmlDataVirtualNode.IsOnNode(XmlNode nodeToCheck)
        {
            RealFoliate();
            return nodeToCheck == _node;
        }
 
        bool IXmlDataVirtualNode.IsOnColumn(DataColumn? col)
        {
            RealFoliate();
            return col == _column;
        }
 
        void IXmlDataVirtualNode.OnFoliated(XmlNode foliatedNode)
        {
            // update the pointer if the element node has been foliated
            if (_node == foliatedNode)
            {
                // if already on this node, nothing to do!
                if (_column == null)
                    return;
                _bNeedFoliate = true;
            }
        }
 
        private void RealFoliate()
        {
            if (!_bNeedFoliate)
                return;
 
            _bNeedFoliate = false;
 
            Debug.Assert(_column != null);
 
            XmlNode? n;
 
            if (_doc.IsTextOnly(_column))
                n = _node.FirstChild;
            else
            {
                if (_column.ColumnMapping == MappingType.Attribute)
                {
                    n = _node.Attributes!.GetNamedItem(_column.EncodedColumnName, _column.Namespace);
                }
                else
                {
                    for (n = _node.FirstChild; n != null; n = n.NextSibling)
                    {
                        if (n.LocalName == _column.EncodedColumnName && n.NamespaceURI == _column.Namespace)
                            break;
                    }
                }
 
                if (n != null && _fOnValue)
                    n = n.FirstChild;
            }
 
            if (n == null)
                throw new InvalidOperationException(SR.DataDom_Foliation);
 
            // Cannot use MoveTo( n ); b/c the initial state for MoveTo is invalid (region is foliated but this is not)
            _node = n;
            _column = null;
            _fOnValue = false;
            AssertValid();
            _bNeedFoliate = false;
        }
 
 
        //The function only helps to find out if there is a namespace declaration of given name is defined on the given node
        //It will not check the ancestor of the given node.
        [RequiresUnreferencedCode(DataSet.RequiresUnreferencedCodeMessage)]
        [RequiresDynamicCode(DataSet.RequiresDynamicCodeMessage)]
        private string? GetNamespace(XmlBoundElement be, string name)
        {
            if (be == null)
                return null;
            XmlAttribute? attr;
            if (be.IsFoliated)
            {
                attr = be.GetAttributeNode(name, StrReservedXmlns);
                if (attr != null)
                    return attr.Value;
                else
                    return null;
            }
            else
            { //defoliated so that we need to search through its column
                DataRow? curRow = be.Row;
                if (curRow == null)
                    return null;
                //going through its attribute columns
                DataColumn? curCol = PreviousColumn(curRow, null, true);
                while (curCol != null)
                {
                    if (curCol.Namespace == StrReservedXmlns)
                    {
                        DataRowVersion rowVersion = (curRow.RowState == DataRowState.Detached) ? DataRowVersion.Proposed : DataRowVersion.Current;
                        return curCol.ConvertObjectToXml(curRow[curCol, rowVersion]);
                    }
                    curCol = PreviousColumn(curRow, curCol, true);
                }
                return null;
            }
        }
 
        [RequiresUnreferencedCode(DataSet.RequiresUnreferencedCodeMessage)]
        [RequiresDynamicCode(DataSet.RequiresDynamicCodeMessage)]
        internal string GetNamespace(string name)
        {
            //we are checking the namespace nodes backwards comparing its normal order in DOM tree
            if (name == "xml")
                return StrReservedXml;
            if (name == "xmlns")
                return StrReservedXmlns;
            if (name != null && name.Length == 0)
                name = "xmlns";
            RealFoliate();
            XmlNode? node = _node;
            XmlNodeType nt;
            string? retVal;
            while (node != null)
            {
                //first identify an element node in the ancestor + itself
                while (node != null && ((nt = node.NodeType) != XmlNodeType.Element))
                {
                    if (nt == XmlNodeType.Attribute)
                        node = ((XmlAttribute)node).OwnerElement;
                    else
                        node = node.ParentNode;
                }
                //found one -- inside if
                if (node != null)
                {
                    //must be element node
                    retVal = GetNamespace((XmlBoundElement)node, name!);
                    if (retVal != null)
                        return retVal;
                    //didn't find it, try the next parentnode
                    node = node.ParentNode;
                }
            }
            //nothing happens, then return string.empty.
            return string.Empty;
        }
 
        internal bool MoveToNamespace(string name)
        {
            _parentOfNS = _node as XmlBoundElement;
            //only need to check with _node, even if _column is not null and its mapping type is element, it can't have attributes
            if (_parentOfNS == null)
                return false;
            RealFoliate();
            XmlNode? node = _node;
            XmlAttribute? attr;
            XmlBoundElement? be;
            while (node != null)
            {
                //check current element node
                be = node as XmlBoundElement;
                if (be != null)
                {
                    if (be.IsFoliated)
                    {
                        attr = be.GetAttributeNode(name, StrReservedXmlns);
                        if (attr != null)
                        {
                            MoveTo(attr);
                            return true;
                        }
                    }
                    else
                    {//defoliated so that we need to search through its column
                        DataRow? curRow = be.Row;
                        if (curRow == null)
                            return false;
                        //going through its attribute columns
                        DataColumn? curCol = PreviousColumn(curRow, null, true);
                        while (curCol != null)
                        {
                            if (curCol.Namespace == StrReservedXmlns && curCol.ColumnName == name)
                            {
                                MoveTo(be, curCol, false);
                                return true;
                            }
                            curCol = PreviousColumn(curRow, curCol, true);
                        }
                    }
                }
                //didn't find it, try the next element ancestor.
                do
                {
                    node = node.ParentNode;
                } while (node != null && node.NodeType != XmlNodeType.Element);
            }
            //nothing happens, the name doesn't exist as a namespace node.
            _parentOfNS = null;
            return false;
        }
 
        //the function will find the next namespace node on the given bound element starting with the given column or attribute
        // whether to use column or attribute depends on if the bound element is foliated or not.
        [RequiresUnreferencedCode(DataSet.RequiresUnreferencedCodeMessage)]
        [RequiresDynamicCode(DataSet.RequiresDynamicCodeMessage)]
        private bool MoveToNextNamespace(XmlBoundElement? be, DataColumn? col, XmlAttribute? curAttr)
        {
            if (be != null)
            {
                if (be.IsFoliated)
                {
                    XmlAttributeCollection attrs = be.Attributes;
                    XmlAttribute? attr = null;
                    bool bFound = false;
                    if (curAttr == null)
                        bFound = true; //the first namespace will be the one
#if DEBUG
                    if (curAttr != null)
                        Debug.Assert(curAttr.NamespaceURI == StrReservedXmlns);
#endif
                    Debug.Assert(attrs != null);
                    int attrInd = attrs.Count;
                    while (attrInd > 0)
                    {
                        attrInd--;
                        attr = attrs[attrInd];
                        if (bFound && attr.NamespaceURI == StrReservedXmlns && !DuplicateNS(be, attr.LocalName))
                        {
                            MoveTo(attr);
                            return true;
                        }
                        if (attr == curAttr)
                            bFound = true;
                    }
                }
                else
                {//defoliated so that we need to search through its column
                    DataRow? curRow = be.Row;
                    if (curRow == null)
                        return false;
                    //going through its attribute columns
                    DataColumn? curCol = PreviousColumn(curRow, col, true);
                    while (curCol != null)
                    {
                        if (curCol.Namespace == StrReservedXmlns && !DuplicateNS(be, curCol.ColumnName))
                        {
                            MoveTo(be, curCol, false);
                            return true;
                        }
                        curCol = PreviousColumn(curRow, curCol, true);
                    }
                }
            }
            return false;
        }
 
        //Caller( DataDocumentXPathNavigator will make sure that the node is at the right position for this call )
        [RequiresUnreferencedCode(DataSet.RequiresUnreferencedCodeMessage)]
        [RequiresDynamicCode(DataSet.RequiresDynamicCodeMessage)]
        internal bool MoveToFirstNamespace(XPathNamespaceScope namespaceScope)
        {
            RealFoliate();
            _parentOfNS = _node as XmlBoundElement;
            //only need to check with _node, even if _column is not null and its mapping type is element, it can't have attributes
            if (_parentOfNS == null)
                return false;
            XmlNode? node = _node;
            XmlBoundElement? be;
            while (node != null)
            {
                be = node as XmlBoundElement;
                if (MoveToNextNamespace(be, null, null))
                    return true;
                //didn't find it
                if (namespaceScope == XPathNamespaceScope.Local)
                    goto labelNoNS;
                //try the next element ancestor.
                do
                {
                    node = node.ParentNode;
                } while (node != null && node.NodeType != XmlNodeType.Element);
            }
            if (namespaceScope == XPathNamespaceScope.All)
            {
                MoveTo(_doc._attrXml, null, false);
                return true;
            }
        labelNoNS:
            //didn't find one namespace node
            _parentOfNS = null;
            return false;
        }
 
        //endElem is on the path from startElem to root is enforced by the caller
        [RequiresUnreferencedCode(DataSet.RequiresUnreferencedCodeMessage)]
        [RequiresDynamicCode(DataSet.RequiresDynamicCodeMessage)]
        private bool DuplicateNS(XmlBoundElement endElem, string lname)
        {
            if (_parentOfNS == null || endElem == null)
                return false;
            XmlBoundElement? be = _parentOfNS;
            XmlNode? node;
            while (be != null && be != endElem)
            {
                if (GetNamespace(be, lname) != null)
                    return true;
                node = be;
                do
                {
                    node = node.ParentNode;
                } while (node != null && node.NodeType != XmlNodeType.Element);
                be = node as XmlBoundElement;
            }
            return false;
        }
 
        //Caller( DataDocumentXPathNavigator will make sure that the node is at the right position for this call )
        [RequiresUnreferencedCode(DataSet.RequiresUnreferencedCodeMessage)]
        [RequiresDynamicCode(DataSet.RequiresDynamicCodeMessage)]
        internal bool MoveToNextNamespace(XPathNamespaceScope namespaceScope)
        {
            RealFoliate();
            Debug.Assert(_parentOfNS != null);
            XmlNode? node = _node;
            //first check within the same boundelement
            if (_column != null)
            {
                Debug.Assert(_column.Namespace == StrReservedXmlns);
                if (namespaceScope == XPathNamespaceScope.Local && _parentOfNS != _node) //already outside scope
                    return false;
                XmlBoundElement? be = _node as XmlBoundElement;
                Debug.Assert(be != null);
                DataRow? curRow = be.Row;
                Debug.Assert(curRow != null);
                DataColumn? curCol = PreviousColumn(curRow, _column, true);
                while (curCol != null)
                {
                    if (curCol.Namespace == StrReservedXmlns)
                    {
                        MoveTo(be, curCol, false);
                        return true;
                    }
                    curCol = PreviousColumn(curRow, curCol, true);
                }
                //didn't find it in this loop
                if (namespaceScope == XPathNamespaceScope.Local)
                    return false;
                //try its ancestor
                do
                {
                    node = node.ParentNode;
                } while (node != null && node.NodeType != XmlNodeType.Element);
            }
            else if (_node.NodeType == XmlNodeType.Attribute)
            {
                XmlAttribute attr = (XmlAttribute)(_node);
                Debug.Assert(attr != null);
                node = attr.OwnerElement;
                if (node == null)
                    return false;
                if (namespaceScope == XPathNamespaceScope.Local && _parentOfNS != node) //already outside scope
                    return false;
                if (MoveToNextNamespace((XmlBoundElement)node, null, attr))
                    return true;
                //didn't find it
                if (namespaceScope == XPathNamespaceScope.Local)
                    return false;
                do
                {
                    node = node.ParentNode;
                } while (node != null && node.NodeType != XmlNodeType.Element);
            }
            // till now, node should be the next ancestor (bound) element of the element parent of current namespace node (attribute or data column)
            while (node != null)
            {
                //try the namespace attributes from the same element
                XmlBoundElement? be = node as XmlBoundElement;
                if (MoveToNextNamespace(be, null, null))
                    return true;
                //no more namespace attribute under the same element
                do
                {
                    node = node.ParentNode;
                } while (node != null && node.NodeType == XmlNodeType.Element);
            }
            //didn't find the next namespace, thus return
            if (namespaceScope == XPathNamespaceScope.All)
            {
                MoveTo(_doc._attrXml, null, false);
                return true;
            }
            return false;
        }
 
        [Conditional("DEBUG")]
        private void AssertValid()
        {
            // This pointer must be int the document list
            //RealFoliate();
            _doc.AssertPointerPresent(this);
            if (_column != null)
            {
                // We must be on a de-foliated region
                XmlBoundElement? rowElem = _node as XmlBoundElement;
                Debug.Assert(rowElem != null);
 
                DataRow? row = rowElem.Row;
                Debug.Assert(row != null);
 
                // We cannot be on a column for which the value is DBNull
                DataRowVersion rowVersion = (row.RowState == DataRowState.Detached) ? DataRowVersion.Proposed : DataRowVersion.Current;
                Debug.Assert(!Convert.IsDBNull(row[_column, rowVersion]));
 
                // If we are on the Text column, we should always have _fOnValue == true
                Debug.Assert((_column.ColumnMapping == MappingType.SimpleContent) ? _fOnValue : true);
            }
            if (_column == null)
                Debug.Assert(!_fOnValue);
        }
 
        internal XmlDataDocument Document { get { return _doc; } }
 
        bool IXmlDataVirtualNode.IsInUse()
        {
            return _owner.IsAlive;
        }
    }
}