Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / cdf / src / NetFx40 / System.Activities / System / Activities / Expressions / Subtract.cs / 1305376 / Subtract.cs
//---------------------------------------------------------------- // Copyright (c) Microsoft Corporation. All rights reserved. //--------------------------------------------------------------- namespace System.Activities.Expressions { using System.Activities; using System.Activities.Statements; using System.Linq.Expressions; using System.Activities.Validation; using System.Collections.Generic; using System.ComponentModel; using System.Runtime; public sealed class Subtract: CodeActivity { //Lock is not needed for operationFunction here. The reason is that delegates for a given Subtract 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 checkedOperationFunction; static Func uncheckedOperationFunction; bool checkedOperation = true; [RequiredArgument] [DefaultValue(null)] public InArgument Left { get; set; } [RequiredArgument] [DefaultValue(null)] public InArgument Right { get; set; } [DefaultValue(true)] public bool Checked { get { return this.checkedOperation; } set { this.checkedOperation = value; } } protected override void CacheMetadata(CodeActivityMetadata metadata) { BinaryExpressionHelper.OnGetArguments(metadata, this.Left, this.Right); if (this.checkedOperation) { EnsureOperationFunction(metadata, ref checkedOperationFunction, ExpressionType.SubtractChecked); } else { EnsureOperationFunction(metadata, ref uncheckedOperationFunction, ExpressionType.Subtract); } } void EnsureOperationFunction(CodeActivityMetadata metadata, ref Func operationFunction, ExpressionType operatorType) { if (operationFunction == null) { ValidationError validationError; if (!BinaryExpressionHelper.TryGenerateLinqDelegate( operatorType, out operationFunction, out validationError)) { metadata.AddValidationError(validationError); } } } protected override TResult Execute(CodeActivityContext context) { TLeft leftValue = this.Left.Get(context); TRight rightValue = this.Right.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(leftValue, rightValue); } else { return uncheckedOperationFunction(leftValue, rightValue); } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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