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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.ComponentModel;
using System.ComponentModel.Design.Serialization;
using System.Globalization;
using System.Reflection;
namespace System.Windows.Forms;
/// <summary>
/// ListViewGroupConverter is a class that can be used to convert ListViewGroup objects
/// from one data type to another. Access this class through the TypeDescriptor.
/// </summary>
internal class ListViewGroupConverter : TypeConverter
{
/// <summary>
/// Determines if this converter can convert an object in the given source type to
/// the native type of the converter.
/// </summary>
public override bool CanConvertFrom(ITypeDescriptorContext? context, Type sourceType)
{
if (sourceType == typeof(string) && context is not null && context.Instance is ListViewItem)
{
return true;
}
return base.CanConvertFrom(context, sourceType);
}
/// <summary>
/// Gets a value indicating whether this converter can convert an object to the given
/// destination type using the context.
/// </summary>
public override bool CanConvertTo(ITypeDescriptorContext? context, Type? destinationType)
{
if (destinationType == typeof(InstanceDescriptor))
{
return true;
}
if (destinationType == typeof(string) && context is not null && context.Instance is ListViewItem)
{
return true;
}
return base.CanConvertTo(context, destinationType);
}
/// <summary>
/// Converts the given object to the converter's native type.
/// </summary>
public override object? ConvertFrom(ITypeDescriptorContext? context, CultureInfo? culture, object value)
{
if (value is string stringValue)
{
string text = stringValue.Trim();
if (context is not null && context.Instance is not null)
{
if (context.Instance is ListViewItem item && item.ListView is not null)
{
foreach (ListViewGroup group in item.ListView.Groups)
{
if (group.Header == text)
{
return group;
}
}
}
}
}
if (value is null || value.Equals(SR.toStringNone))
{
return null;
}
return base.ConvertFrom(context, culture, value);
}
/// <summary>
/// Converts the given object to another type. The most common types to convert
/// are to and from a string object. The default implementation will make a call
/// to ToString on the object if the object is valid and if the destination
/// type is string. If this cannot convert to the destination type, this will
/// throw a NotSupportedException.
/// </summary>
public override object? ConvertTo(ITypeDescriptorContext? context, CultureInfo? culture, object? value, Type destinationType)
{
ArgumentNullException.ThrowIfNull(destinationType);
if (destinationType == typeof(InstanceDescriptor) && value is ListViewGroup group)
{
// Header
ConstructorInfo ctor = typeof(ListViewGroup).GetConstructor([typeof(string), typeof(HorizontalAlignment)])!;
Debug.Assert(ctor is not null, "Expected the constructor to exist.");
return new InstanceDescriptor(ctor, new object[] { group.Header, group.HeaderAlignment }, false);
}
if (destinationType == typeof(string) && value is null)
{
return SR.toStringNone;
}
return base.ConvertTo(context, culture, value, destinationType);
}
/// <summary>
/// Retrieves a collection containing a set of standard values for the data type this
/// validator is designed for. This will return null if the data type does not support
/// a standard set of values.
/// </summary>
public override StandardValuesCollection? GetStandardValues(ITypeDescriptorContext? context)
{
if (context is not null && context.Instance is ListViewItem item && item.ListView is not null)
{
List<ListViewGroup?> list = new();
foreach (ListViewGroup group in item.ListView.Groups)
{
list.Add(group);
}
list.Add(null);
return new StandardValuesCollection(list);
}
return null;
}
/// <summary>
/// Determines if the list of standard values returned from GetStandardValues is an
/// exclusive list. If the list is exclusive, then no other values are valid, such as
/// in an enum data type. If the list is not exclusive, then there are other valid values
/// besides the list of standard values GetStandardValues provides.
/// </summary>
public override bool GetStandardValuesExclusive(ITypeDescriptorContext? context)
{
return true;
}
/// <summary>
/// Determines if this object supports a standard set of values that can be picked
/// from a list.
/// </summary>
public override bool GetStandardValuesSupported(ITypeDescriptorContext? context)
{
return true;
}
}
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