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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.Linq.Expressions;
using System.Runtime;
public sealed class Cast<TOperand, TResult> : CodeActivity<TResult>
{
//Lock is not needed for operationFunction here. The reason is that delegates for a given Cast<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> checkedOperationFunction;
static Func<TOperand, TResult> uncheckedOperationFunction;
bool checkedOperation = true;
[RequiredArgument]
[DefaultValue(null)]
public InArgument<TOperand> Operand
{
get;
set;
}
[DefaultValue(true)]
public bool Checked
{
get { return this.checkedOperation; }
set { this.checkedOperation = value; }
}
protected override void CacheMetadata(CodeActivityMetadata metadata)
{
UnaryExpressionHelper.OnGetArguments(metadata, this.Operand);
if (this.checkedOperation)
{
EnsureOperationFunction(metadata, ref checkedOperationFunction, ExpressionType.ConvertChecked);
}
else
{
EnsureOperationFunction(metadata, ref uncheckedOperationFunction, ExpressionType.Convert);
}
}
void EnsureOperationFunction(CodeActivityMetadata metadata,
ref Func<TOperand, TResult> operationFunction,
ExpressionType operatorType)
{
if (operationFunction == null)
{
ValidationError validationError;
if (!UnaryExpressionHelper.TryGenerateLinqDelegate(
operatorType,
out operationFunction,
out validationError))
{
metadata.AddValidationError(validationError);
}
}
}
protected override TResult Execute(CodeActivityContext context)
{
TOperand operandValue = this.Operand.Get(context);
//if user changed Checked flag between Open and Execution,
//a NRE may be thrown and that's by design
if (this.checkedOperation)
{
return checkedOperationFunction(operandValue);
}
else
{
return uncheckedOperationFunction(operandValue);
}
}
}
}
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