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//----------------------------------------------------------------
// Copyright (c) Microsoft Corporation. All rights reserved.
//----------------------------------------------------------------
namespace System.Activities.Expressions
{
using System.Activities;
using System.Activities.Statements;
using System.Activities.Validation;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics.CodeAnalysis;
using System.Linq.Expressions;
using System.Runtime;
[SuppressMessage(FxCop.Category.Naming, FxCop.Rule.IdentifiersShouldNotMatchKeywords,
Justification = "Optimizing for XAML naming. VB imperative users will [] qualify (e.g. New [As])")]
public sealed class As<TOperand, TResult> : CodeActivity<TResult>
{
//Lock is not needed for operationFunction here. The reason is that delegates for a given As<TLeft, TRight, TResult> are the same.
//It's possible that 2 threads are assigning the operationFucntion at the same time. But it's okay because the compiled codes are the same.
static Func<TOperand, TResult> operationFunction;
[RequiredArgument]
[DefaultValue(null)]
public InArgument<TOperand> Operand
{
get;
set;
}
protected override void CacheMetadata(CodeActivityMetadata metadata)
{
UnaryExpressionHelper.OnGetArguments(metadata, this.Operand);
if (operationFunction == null)
{
ValidationError validationError;
if (!UnaryExpressionHelper.TryGenerateLinqDelegate(ExpressionType.TypeAs, out operationFunction, out validationError))
{
metadata.AddValidationError(validationError);
}
}
}
protected override TResult Execute(CodeActivityContext context)
{
Fx.Assert(operationFunction != null, "OperationFunction must exist.");
TOperand operandValue = this.Operand.Get(context);
return operationFunction(operandValue);
}
}
}
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