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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.Collections.ObjectModel;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Dynamic.Utils;
using System.Reflection;
using System.Runtime.CompilerServices;
namespace System.Linq.Expressions
{
/// <summary>
/// Represents a constructor call that has a collection initializer.
/// </summary>
/// <remarks>
/// Use the <see cref="Expression.ListInit(NewExpression, Expression[])"/> factory methods to create a ListInitExpression.
/// The value of the <see cref="NodeType" /> property of a ListInitExpression is ListInit.
/// </remarks>
[DebuggerTypeProxy(typeof(ListInitExpressionProxy))]
public sealed class ListInitExpression : Expression
{
internal ListInitExpression(NewExpression newExpression, ReadOnlyCollection<ElementInit> initializers)
{
NewExpression = newExpression;
Initializers = initializers;
}
/// <summary>
/// Returns the node type of this <see cref="Expression"/>. (Inherited from <see cref="Expression"/>.)
/// </summary>
/// <returns>The <see cref="ExpressionType"/> that represents this expression.</returns>
public sealed override ExpressionType NodeType => ExpressionType.ListInit;
/// <summary>
/// Gets the static type of the expression that this <see cref="Expression"/> represents. (Inherited from <see cref="Expression"/>.)
/// </summary>
/// <returns>The <see cref="System.Type"/> that represents the static type of the expression.</returns>
public sealed override Type Type => NewExpression.Type;
/// <summary>
/// Gets a value that indicates whether the expression tree node can be reduced.
/// </summary>
public override bool CanReduce => true;
/// <summary>
/// Gets the expression that contains a call to the constructor of a collection type.
/// </summary>
public NewExpression NewExpression { get; }
/// <summary>
/// Gets the element initializers that are used to initialize a collection.
/// </summary>
public ReadOnlyCollection<ElementInit> Initializers { get; }
/// <summary>
/// Dispatches to the specific visit method for this node type.
/// </summary>
protected internal override Expression Accept(ExpressionVisitor visitor)
{
return visitor.VisitListInit(this);
}
/// <summary>
/// Reduces the binary expression node to a simpler expression.
/// If CanReduce returns true, this should return a valid expression.
/// This method is allowed to return another node which itself
/// must be reduced.
/// </summary>
/// <returns>The reduced expression.</returns>
public override Expression Reduce()
{
return MemberInitExpression.ReduceListInit(NewExpression, Initializers, keepOnStack: true);
}
/// <summary>
/// Creates a new expression that is like this one, but using the
/// supplied children. If all of the children are the same, it will
/// return this expression.
/// </summary>
/// <param name="newExpression">The <see cref="NewExpression"/> property of the result.</param>
/// <param name="initializers">The <see cref="Initializers"/> property of the result.</param>
/// <returns>This expression if no children changed, or an expression with the updated children.</returns>
public ListInitExpression Update(NewExpression newExpression, IEnumerable<ElementInit> initializers)
{
if (newExpression == NewExpression && initializers != null)
{
if (ExpressionUtils.SameElements(ref initializers!, Initializers))
{
return this;
}
}
return ListInit(newExpression, initializers!);
}
}
public partial class Expression
{
/// <summary>
/// Creates a <see cref="ListInitExpression"/> that uses a method named "Add" to add elements to a collection.
/// </summary>
/// <param name="newExpression">A <see cref="NewExpression"/> to set the <see cref="ListInitExpression.NewExpression"/> property equal to.</param>
/// <param name="initializers">An array of <see cref="Expression"/> objects to use to populate the <see cref="ListInitExpression.Initializers"/> collection.</param>
/// <returns>A <see cref="ListInitExpression"/> that has the <see cref="NodeType"/> property equal to <see cref="ExpressionType.ListInit"/> and the <see cref="ListInitExpression.NewExpression"/> property set to the specified value.</returns>
[RequiresUnreferencedCode(ExpressionRequiresUnreferencedCode)]
[RequiresDynamicCode(GenericMethodRequiresDynamicCode)]
public static ListInitExpression ListInit(NewExpression newExpression, params Expression[] initializers)
{
return ListInit(newExpression, initializers as IEnumerable<Expression>);
}
/// <summary>
/// Creates a <see cref="ListInitExpression"/> that uses a method named "Add" to add elements to a collection.
/// </summary>
/// <param name="newExpression">A <see cref="NewExpression"/> to set the <see cref="ListInitExpression.NewExpression"/> property equal to.</param>
/// <param name="initializers">An <see cref="IEnumerable{T}"/> that contains <see cref="Expressions.ElementInit"/> objects to use to populate the <see cref="ListInitExpression.Initializers"/> collection.</param>
/// <returns>A <see cref="ListInitExpression"/> that has the <see cref="NodeType"/> property equal to <see cref="ExpressionType.ListInit"/> and the <see cref="ListInitExpression.NewExpression"/> property set to the specified value.</returns>
[RequiresUnreferencedCode(ExpressionRequiresUnreferencedCode)]
[RequiresDynamicCode(GenericMethodRequiresDynamicCode)]
public static ListInitExpression ListInit(NewExpression newExpression, IEnumerable<Expression> initializers)
{
ArgumentNullException.ThrowIfNull(newExpression);
ArgumentNullException.ThrowIfNull(initializers);
ReadOnlyCollection<Expression> initializerlist = initializers.ToReadOnly();
if (initializerlist.Count == 0)
{
return new ListInitExpression(newExpression, ReadOnlyCollection<ElementInit>.Empty);
}
MethodInfo? addMethod = FindMethod(newExpression.Type, "Add", null, new Expression[] { initializerlist[0] }, BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
return ListInit(newExpression, addMethod, initializerlist);
}
/// <summary>
/// Creates a <see cref="ListInitExpression"/> that uses a specified method to add elements to a collection.
/// </summary>
/// <param name="newExpression">A <see cref="NewExpression"/> to set the <see cref="ListInitExpression.NewExpression"/> property equal to.</param>
/// <param name="addMethod">A <see cref="MethodInfo"/> that represents an instance method named "Add" (case insensitive), that adds an element to a collection.</param>
/// <param name="initializers">An array of <see cref="Expression"/> objects to use to populate the <see cref="ListInitExpression.Initializers"/> collection.</param>
/// <returns>A <see cref="ListInitExpression"/> that has the <see cref="NodeType"/> property equal to <see cref="ExpressionType.ListInit"/> and the <see cref="ListInitExpression.NewExpression"/> property set to the specified value.</returns>
[RequiresUnreferencedCode(ExpressionRequiresUnreferencedCode)]
[RequiresDynamicCode(GenericMethodRequiresDynamicCode)]
public static ListInitExpression ListInit(NewExpression newExpression, MethodInfo? addMethod, params Expression[] initializers)
{
return ListInit(newExpression, addMethod, initializers as IEnumerable<Expression>);
}
/// <summary>
/// Creates a <see cref="ListInitExpression"/> that uses a specified method to add elements to a collection.
/// </summary>
/// <param name="newExpression">A <see cref="NewExpression"/> to set the <see cref="ListInitExpression.NewExpression"/> property equal to.</param>
/// <param name="addMethod">A <see cref="MethodInfo"/> that represents an instance method named "Add" (case insensitive), that adds an element to a collection.</param>
/// <param name="initializers">An <see cref="IEnumerable{T}"/> that contains <see cref="Expression"/> objects to use to populate the Initializers collection.</param>
/// <returns>A <see cref="ListInitExpression"/> that has the <see cref="NodeType"/> property equal to <see cref="ExpressionType.ListInit"/> and the <see cref="ListInitExpression.NewExpression"/> property set to the specified value.</returns>
[RequiresUnreferencedCode(ExpressionRequiresUnreferencedCode)]
[RequiresDynamicCode(GenericMethodRequiresDynamicCode)]
public static ListInitExpression ListInit(NewExpression newExpression, MethodInfo? addMethod, IEnumerable<Expression> initializers)
{
if (addMethod == null)
{
return ListInit(newExpression, initializers);
}
ArgumentNullException.ThrowIfNull(newExpression);
ArgumentNullException.ThrowIfNull(initializers);
ReadOnlyCollection<Expression> initializerlist = initializers.ToReadOnly();
ElementInit[] initList = new ElementInit[initializerlist.Count];
for (int i = 0; i < initializerlist.Count; i++)
{
initList[i] = ElementInit(addMethod, initializerlist[i]);
}
return ListInit(newExpression, new TrueReadOnlyCollection<ElementInit>(initList));
}
/// <summary>
/// Creates a <see cref="ListInitExpression"/> that uses specified <see cref="Expressions.ElementInit"/> objects to initialize a collection.
/// </summary>
/// <param name="newExpression">A <see cref="NewExpression"/> to set the <see cref="ListInitExpression.NewExpression"/> property equal to.</param>
/// <param name="initializers">An array that contains <see cref="Expressions.ElementInit"/> objects to use to populate the <see cref="ListInitExpression.Initializers"/> collection.</param>
/// <returns>
/// A <see cref="ListInitExpression"/> that has the <see cref="NodeType"/> property equal to <see cref="ExpressionType.ListInit"/>
/// and the <see cref="ListInitExpression.NewExpression"/> and <see cref="ListInitExpression.Initializers"/> properties set to the specified values.
/// </returns>
/// <remarks>
/// The <see cref="Type"/> property of <paramref name="newExpression"/> must represent a type that implements <see cref="Collections.IEnumerable"/>.
/// The <see cref="Type"/> property of the resulting <see cref="ListInitExpression"/> is equal to <paramref name="newExpression"/>.Type.
/// </remarks>
public static ListInitExpression ListInit(NewExpression newExpression, params ElementInit[] initializers)
{
return ListInit(newExpression, (IEnumerable<ElementInit>)initializers);
}
/// <summary>
/// Creates a <see cref="ListInitExpression"/> that uses specified <see cref="Expressions.ElementInit"/> objects to initialize a collection.
/// </summary>
/// <param name="newExpression">A <see cref="NewExpression"/> to set the <see cref="ListInitExpression.NewExpression"/> property equal to.</param>
/// <param name="initializers">An <see cref="IEnumerable{T}"/> that contains <see cref="Expressions.ElementInit"/> objects to use to populate the <see cref="ListInitExpression.Initializers"/> collection.</param>
/// <returns>An <see cref="IEnumerable{T}"/> that contains <see cref="Expressions.ElementInit"/> objects to use to populate the <see cref="ListInitExpression.Initializers"/> collection.</returns>
/// <remarks>
/// The <see cref="Type"/> property of <paramref name="newExpression"/> must represent a type that implements <see cref="Collections.IEnumerable"/>.
/// The <see cref="Type"/> property of the resulting <see cref="ListInitExpression"/> is equal to <paramref name="newExpression"/>.Type.
/// </remarks>
public static ListInitExpression ListInit(NewExpression newExpression, IEnumerable<ElementInit> initializers)
{
ArgumentNullException.ThrowIfNull(newExpression);
ArgumentNullException.ThrowIfNull(initializers);
ReadOnlyCollection<ElementInit> initializerlist = initializers.ToReadOnly();
ValidateListInitArgs(newExpression.Type, initializerlist, nameof(newExpression));
return new ListInitExpression(newExpression, initializerlist);
}
}
}
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