86 lines
3.0 KiB
C#
86 lines
3.0 KiB
C#
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//----------------------------------------------------------------
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// Copyright (c) Microsoft Corporation. All rights reserved.
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//----------------------------------------------------------------
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namespace System.Activities.Expressions
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{
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using System.Activities;
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using System.Activities.Statements;
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using System.Activities.Validation;
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using System.Collections.Generic;
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using System.ComponentModel;
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using System.Linq.Expressions;
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using System.Runtime;
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public sealed class Cast<TOperand, TResult> : CodeActivity<TResult>
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{
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//Lock is not needed for operationFunction here. The reason is that delegates for a given Cast<TLeft, TRight, TResult> are the same.
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//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.
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static Func<TOperand, TResult> checkedOperationFunction;
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static Func<TOperand, TResult> uncheckedOperationFunction;
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bool checkedOperation = true;
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[RequiredArgument]
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[DefaultValue(null)]
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public InArgument<TOperand> Operand
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{
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get;
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set;
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}
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[DefaultValue(true)]
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public bool Checked
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{
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get { return this.checkedOperation; }
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set { this.checkedOperation = value; }
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}
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protected override void CacheMetadata(CodeActivityMetadata metadata)
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{
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UnaryExpressionHelper.OnGetArguments(metadata, this.Operand);
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if (this.checkedOperation)
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{
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EnsureOperationFunction(metadata, ref checkedOperationFunction, ExpressionType.ConvertChecked);
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}
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else
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{
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EnsureOperationFunction(metadata, ref uncheckedOperationFunction, ExpressionType.Convert);
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}
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}
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void EnsureOperationFunction(CodeActivityMetadata metadata,
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ref Func<TOperand, TResult> operationFunction,
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ExpressionType operatorType)
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{
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if (operationFunction == null)
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{
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ValidationError validationError;
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if (!UnaryExpressionHelper.TryGenerateLinqDelegate(
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operatorType,
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out operationFunction,
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out validationError))
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{
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metadata.AddValidationError(validationError);
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}
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}
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}
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protected override TResult Execute(CodeActivityContext context)
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{
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TOperand operandValue = this.Operand.Get(context);
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//if user changed Checked flag between Open and Execution,
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//a NRE may be thrown and that's by design
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if (this.checkedOperation)
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{
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return checkedOperationFunction(operandValue);
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}
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else
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{
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return uncheckedOperationFunction(operandValue);
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}
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}
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}
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}
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