54 lines
2.1 KiB
C#
54 lines
2.1 KiB
C#
//----------------------------------------------------------------
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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.Diagnostics.CodeAnalysis;
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using System.Linq.Expressions;
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using System.Runtime;
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[SuppressMessage(FxCop.Category.Naming, FxCop.Rule.IdentifiersShouldNotMatchKeywords,
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Justification = "Optimizing for XAML naming. VB imperative users will [] qualify (e.g. New [As])")]
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public sealed class As<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 As<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> operationFunction;
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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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protected override void CacheMetadata(CodeActivityMetadata metadata)
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{
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UnaryExpressionHelper.OnGetArguments(metadata, this.Operand);
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if (operationFunction == null)
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{
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ValidationError validationError;
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if (!UnaryExpressionHelper.TryGenerateLinqDelegate(ExpressionType.TypeAs, out operationFunction, 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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Fx.Assert(operationFunction != null, "OperationFunction must exist.");
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TOperand operandValue = this.Operand.Get(context);
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return operationFunction(operandValue);
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}
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}
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}
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