/* ****************************************************************************
*
* Copyright (c) Microsoft Corporation.
*
* This source code is subject to terms and conditions of the Microsoft Public License. A
* copy of the license can be found in the License.html file at the root of this distribution. If
* you cannot locate the Microsoft Public License, please send an email to
* dlr@microsoft.com. By using this source code in any fashion, you are agreeing to be bound
* by the terms of the Microsoft Public License.
*
* You must not remove this notice, or any other, from this software.
*
*
* ***************************************************************************/
using System;
using System.Diagnostics;
#if CLR2
namespace Microsoft.Scripting.Ast{
#else
namespace System.Linq.Expressions {
#endif
/// <summary>
/// Represents a label, which can be placed in any <see cref="Expression"/> context. If
/// it is jumped to, it will get the value provided by the corresponding
/// <see cref="GotoExpression"/>. Otherwise, it gets the value in <see cref="LabelExpression.DefaultValue"/>. If the
/// <see cref="Type"/> equals System.Void, no value should be provided.
/// </summary>
#if !SILVERLIGHT
[DebuggerTypeProxy(typeof(Expression.LabelExpressionProxy))]
#endif
public sealed class LabelExpression : Expression {
private readonly Expression _defaultValue;
private readonly LabelTarget _target;
internal LabelExpression(LabelTarget label, Expression defaultValue) {
_target = label;
_defaultValue = defaultValue;
}
/// <summary>
/// Gets the static type of the expression that this <see cref="Expression" /> represents. (Inherited from <see cref="Expression"/>.)
/// </summary>
/// <returns>The <see cref="Type"/> that represents the static type of the expression.</returns>
public sealed override Type Type {
get { return _target.Type; }
}
/// <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 {
get { return ExpressionType.Label; }
}
/// <summary>
/// The <see cref="LabelTarget"/> which this label is associated with.
/// </summary>
public LabelTarget Target {
get { return _target; }
}
/// <summary>
/// The value of the <see cref="LabelExpression"/> when the label is reached through
/// normal control flow (e.g. is not jumped to).
/// </summary>
public Expression DefaultValue {
get { return _defaultValue; }
}
/// <summary>
/// Dispatches to the specific visit method for this node type.
/// </summary>
protected internal override Expression Accept(ExpressionVisitor visitor) {
return visitor.VisitLabel(this);
}
/// <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="target">The <see cref="Target" /> property of the result.</param>
/// <param name="defaultValue">The <see cref="DefaultValue" /> property of the result.</param>
/// <returns>This expression if no children changed, or an expression with the updated children.</returns>
public LabelExpression Update(LabelTarget target, Expression defaultValue) {
if (target == Target && defaultValue == DefaultValue) {
return this;
}
return Expression.Label(target, defaultValue);
}
}
public partial class Expression {
/// <summary>
/// Creates a <see cref="LabelExpression"/> representing a label with no default value.
/// </summary>
/// <param name="target">The <see cref="LabelTarget"/> which this <see cref="LabelExpression"/> will be associated with.</param>
/// <returns>A <see cref="LabelExpression"/> with no default value.</returns>
public static LabelExpression Label(LabelTarget target) {
return Label(target, null);
}
/// <summary>
/// Creates a <see cref="LabelExpression"/> representing a label with the given default value.
/// </summary>
/// <param name="target">The <see cref="LabelTarget"/> which this <see cref="LabelExpression"/> will be associated with.</param>
/// <param name="defaultValue">The value of this <see cref="LabelExpression"/> when the label is reached through normal control flow.</param>
/// <returns>A <see cref="LabelExpression"/> with the given default value.</returns>
public static LabelExpression Label(LabelTarget target, Expression defaultValue) {
ValidateGoto(target, ref defaultValue, "label", "defaultValue");
return new LabelExpression(target, defaultValue);
}
}
}
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