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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.Collections.Generic;
using System.Diagnostics;
using System.Dynamic.Utils;
using System.Linq.Expressions;
namespace System.Dynamic
{
/// <summary>
/// Represents the dynamic binding and a binding logic of an object participating in the dynamic binding.
/// </summary>
public class DynamicMetaObject
{
/// <summary>
/// Represents an empty array of type <see cref="DynamicMetaObject"/>. This field is read-only.
/// </summary>
public static readonly DynamicMetaObject[] EmptyMetaObjects = Array.Empty<DynamicMetaObject>();
/// <summary>
/// Initializes a new instance of the <see cref="DynamicMetaObject"/> class.
/// </summary>
/// <param name="expression">The expression representing this <see cref="DynamicMetaObject"/> during the dynamic binding process.</param>
/// <param name="restrictions">The set of binding restrictions under which the binding is valid.</param>
public DynamicMetaObject(Expression expression, BindingRestrictions restrictions)
{
ArgumentNullException.ThrowIfNull(expression);
ArgumentNullException.ThrowIfNull(restrictions);
Expression = expression;
Restrictions = restrictions;
}
/// <summary>
/// Initializes a new instance of the <see cref="DynamicMetaObject"/> class.
/// </summary>
/// <param name="expression">The expression representing this <see cref="DynamicMetaObject"/> during the dynamic binding process.</param>
/// <param name="restrictions">The set of binding restrictions under which the binding is valid.</param>
/// <param name="value">The runtime value represented by the <see cref="DynamicMetaObject"/>.</param>
public DynamicMetaObject(Expression expression, BindingRestrictions restrictions, object value)
: this(expression, restrictions)
{
_value = value;
}
// having sentinel value means having no value. (this way we do not need a separate hasValue field)
private static readonly object s_noValueSentinel = new object();
private readonly object _value = s_noValueSentinel;
/// <summary>
/// The expression representing the <see cref="DynamicMetaObject"/> during the dynamic binding process.
/// </summary>
public Expression Expression { get; }
/// <summary>
/// The set of binding restrictions under which the binding is valid.
/// </summary>
public BindingRestrictions Restrictions { get; }
/// <summary>
/// The runtime value represented by this <see cref="DynamicMetaObject"/>.
/// </summary>
public object? Value => HasValue ? _value : null;
/// <summary>
/// Gets a value indicating whether the <see cref="DynamicMetaObject"/> has the runtime value.
/// </summary>
public bool HasValue => _value != s_noValueSentinel;
/// <summary>
/// Gets the <see cref="Type"/> of the runtime value or null if the <see cref="DynamicMetaObject"/> has no value associated with it.
/// </summary>
public Type? RuntimeType
{
get
{
if (HasValue)
{
Type ct = Expression.Type;
// valuetype at compile time, type cannot change.
if (ct.IsValueType)
{
return ct;
}
return Value?.GetType();
}
else
{
return null;
}
}
}
/// <summary>
/// Gets the limit type of the <see cref="DynamicMetaObject"/>.
/// </summary>
/// <remarks>Represents the most specific type known about the object represented by the <see cref="DynamicMetaObject"/>. <see cref="RuntimeType"/> if runtime value is available, a type of the <see cref="Expression"/> otherwise.</remarks>
public Type LimitType => RuntimeType ?? Expression.Type;
/// <summary>
/// Performs the binding of the dynamic conversion operation.
/// </summary>
/// <param name="binder">An instance of the <see cref="ConvertBinder"/> that represents the details of the dynamic operation.</param>
/// <returns>The new <see cref="DynamicMetaObject"/> representing the result of the binding.</returns>
public virtual DynamicMetaObject BindConvert(ConvertBinder binder)
{
ArgumentNullException.ThrowIfNull(binder);
return binder.FallbackConvert(this);
}
/// <summary>
/// Performs the binding of the dynamic get member operation.
/// </summary>
/// <param name="binder">An instance of the <see cref="GetMemberBinder"/> that represents the details of the dynamic operation.</param>
/// <returns>The new <see cref="DynamicMetaObject"/> representing the result of the binding.</returns>
public virtual DynamicMetaObject BindGetMember(GetMemberBinder binder)
{
ArgumentNullException.ThrowIfNull(binder);
return binder.FallbackGetMember(this);
}
/// <summary>
/// Performs the binding of the dynamic set member operation.
/// </summary>
/// <param name="binder">An instance of the <see cref="SetMemberBinder"/> that represents the details of the dynamic operation.</param>
/// <param name="value">The <see cref="DynamicMetaObject"/> representing the value for the set member operation.</param>
/// <returns>The new <see cref="DynamicMetaObject"/> representing the result of the binding.</returns>
public virtual DynamicMetaObject BindSetMember(SetMemberBinder binder, DynamicMetaObject value)
{
ArgumentNullException.ThrowIfNull(binder);
return binder.FallbackSetMember(this, value);
}
/// <summary>
/// Performs the binding of the dynamic delete member operation.
/// </summary>
/// <param name="binder">An instance of the <see cref="DeleteMemberBinder"/> that represents the details of the dynamic operation.</param>
/// <returns>The new <see cref="DynamicMetaObject"/> representing the result of the binding.</returns>
public virtual DynamicMetaObject BindDeleteMember(DeleteMemberBinder binder)
{
ArgumentNullException.ThrowIfNull(binder);
return binder.FallbackDeleteMember(this);
}
/// <summary>
/// Performs the binding of the dynamic get index operation.
/// </summary>
/// <param name="binder">An instance of the <see cref="GetIndexBinder"/> that represents the details of the dynamic operation.</param>
/// <param name="indexes">An array of <see cref="DynamicMetaObject"/> instances - indexes for the get index operation.</param>
/// <returns>The new <see cref="DynamicMetaObject"/> representing the result of the binding.</returns>
public virtual DynamicMetaObject BindGetIndex(GetIndexBinder binder, DynamicMetaObject[] indexes)
{
ArgumentNullException.ThrowIfNull(binder);
return binder.FallbackGetIndex(this, indexes);
}
/// <summary>
/// Performs the binding of the dynamic set index operation.
/// </summary>
/// <param name="binder">An instance of the <see cref="SetIndexBinder"/> that represents the details of the dynamic operation.</param>
/// <param name="indexes">An array of <see cref="DynamicMetaObject"/> instances - indexes for the set index operation.</param>
/// <param name="value">The <see cref="DynamicMetaObject"/> representing the value for the set index operation.</param>
/// <returns>The new <see cref="DynamicMetaObject"/> representing the result of the binding.</returns>
public virtual DynamicMetaObject BindSetIndex(SetIndexBinder binder, DynamicMetaObject[] indexes, DynamicMetaObject value)
{
ArgumentNullException.ThrowIfNull(binder);
return binder.FallbackSetIndex(this, indexes, value);
}
/// <summary>
/// Performs the binding of the dynamic delete index operation.
/// </summary>
/// <param name="binder">An instance of the <see cref="DeleteIndexBinder"/> that represents the details of the dynamic operation.</param>
/// <param name="indexes">An array of <see cref="DynamicMetaObject"/> instances - indexes for the delete index operation.</param>
/// <returns>The new <see cref="DynamicMetaObject"/> representing the result of the binding.</returns>
public virtual DynamicMetaObject BindDeleteIndex(DeleteIndexBinder binder, DynamicMetaObject[] indexes)
{
ArgumentNullException.ThrowIfNull(binder);
return binder.FallbackDeleteIndex(this, indexes);
}
/// <summary>
/// Performs the binding of the dynamic invoke member operation.
/// </summary>
/// <param name="binder">An instance of the <see cref="InvokeMemberBinder"/> that represents the details of the dynamic operation.</param>
/// <param name="args">An array of <see cref="DynamicMetaObject"/> instances - arguments to the invoke member operation.</param>
/// <returns>The new <see cref="DynamicMetaObject"/> representing the result of the binding.</returns>
public virtual DynamicMetaObject BindInvokeMember(InvokeMemberBinder binder, DynamicMetaObject[] args)
{
ArgumentNullException.ThrowIfNull(binder);
return binder.FallbackInvokeMember(this, args);
}
/// <summary>
/// Performs the binding of the dynamic invoke operation.
/// </summary>
/// <param name="binder">An instance of the <see cref="InvokeBinder"/> that represents the details of the dynamic operation.</param>
/// <param name="args">An array of <see cref="DynamicMetaObject"/> instances - arguments to the invoke operation.</param>
/// <returns>The new <see cref="DynamicMetaObject"/> representing the result of the binding.</returns>
public virtual DynamicMetaObject BindInvoke(InvokeBinder binder, DynamicMetaObject[] args)
{
ArgumentNullException.ThrowIfNull(binder);
return binder.FallbackInvoke(this, args);
}
/// <summary>
/// Performs the binding of the dynamic create instance operation.
/// </summary>
/// <param name="binder">An instance of the <see cref="CreateInstanceBinder"/> that represents the details of the dynamic operation.</param>
/// <param name="args">An array of <see cref="DynamicMetaObject"/> instances - arguments to the create instance operation.</param>
/// <returns>The new <see cref="DynamicMetaObject"/> representing the result of the binding.</returns>
public virtual DynamicMetaObject BindCreateInstance(CreateInstanceBinder binder, DynamicMetaObject[] args)
{
ArgumentNullException.ThrowIfNull(binder);
return binder.FallbackCreateInstance(this, args);
}
/// <summary>
/// Performs the binding of the dynamic unary operation.
/// </summary>
/// <param name="binder">An instance of the <see cref="UnaryOperationBinder"/> that represents the details of the dynamic operation.</param>
/// <returns>The new <see cref="DynamicMetaObject"/> representing the result of the binding.</returns>
public virtual DynamicMetaObject BindUnaryOperation(UnaryOperationBinder binder)
{
ArgumentNullException.ThrowIfNull(binder);
return binder.FallbackUnaryOperation(this);
}
/// <summary>
/// Performs the binding of the dynamic binary operation.
/// </summary>
/// <param name="binder">An instance of the <see cref="BinaryOperationBinder"/> that represents the details of the dynamic operation.</param>
/// <param name="arg">An instance of the <see cref="DynamicMetaObject"/> representing the right hand side of the binary operation.</param>
/// <returns>The new <see cref="DynamicMetaObject"/> representing the result of the binding.</returns>
public virtual DynamicMetaObject BindBinaryOperation(BinaryOperationBinder binder, DynamicMetaObject arg)
{
ArgumentNullException.ThrowIfNull(binder);
return binder.FallbackBinaryOperation(this, arg);
}
/// <summary>
/// Returns the enumeration of all dynamic member names.
/// </summary>
/// <returns>The list of dynamic member names.</returns>
public virtual IEnumerable<string> GetDynamicMemberNames() => Array.Empty<string>();
/// <summary>
/// Returns the list of expressions represented by the <see cref="DynamicMetaObject"/> instances.
/// </summary>
/// <param name="objects">An array of <see cref="DynamicMetaObject"/> instances to extract expressions from.</param>
/// <returns>The array of expressions.</returns>
internal static Expression[] GetExpressions(DynamicMetaObject[] objects)
{
ArgumentNullException.ThrowIfNull(objects);
Expression[] res = new Expression[objects.Length];
for (int i = 0; i < objects.Length; i++)
{
DynamicMetaObject mo = objects[i];
ArgumentNullException.ThrowIfNull(mo, nameof(objects));
Expression expr = mo.Expression;
Debug.Assert(expr != null, "Unexpected null expression; ctor should have caught this.");
res[i] = expr;
}
return res;
}
/// <summary>
/// Creates a meta-object for the specified object.
/// </summary>
/// <param name="value">The object to get a meta-object for.</param>
/// <param name="expression">The expression representing this <see cref="DynamicMetaObject"/> during the dynamic binding process.</param>
/// <returns>
/// If the given object implements <see cref="IDynamicMetaObjectProvider"/> and is not a remote object from outside the current AppDomain,
/// returns the object's specific meta-object returned by <see cref="IDynamicMetaObjectProvider.GetMetaObject"/>. Otherwise a plain new meta-object
/// with no restrictions is created and returned.
/// </returns>
public static DynamicMetaObject Create(object value, Expression expression)
{
ArgumentNullException.ThrowIfNull(expression);
if (value is IDynamicMetaObjectProvider ido)
{
var idoMetaObject = ido.GetMetaObject(expression);
if (idoMetaObject == null ||
!idoMetaObject.HasValue ||
idoMetaObject.Value == null ||
(object)idoMetaObject.Expression != (object)expression)
{
throw System.Linq.Expressions.Error.InvalidMetaObjectCreated(ido.GetType());
}
return idoMetaObject;
}
else
{
return new DynamicMetaObject(expression, BindingRestrictions.Empty, value);
}
}
}
}
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