60 lines
1.9 KiB
C#
60 lines
1.9 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.Linq.Expressions;
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using System.Runtime;
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[Fx.Tag.XamlVisible(false)]
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public class EnvironmentLocationReference<T> : CodeActivity<Location<T>>, IExpressionContainer, ILocationReferenceExpression
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{
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LocationReference locationReference;
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// Ctors are internal because we rely on validation from creator or descendant
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internal EnvironmentLocationReference()
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{
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this.UseOldFastPath = true;
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}
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internal EnvironmentLocationReference(LocationReference locationReference)
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: this()
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{
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this.locationReference = locationReference;
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}
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public virtual LocationReference LocationReference
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{
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get
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{
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return this.locationReference;
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}
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}
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protected override void CacheMetadata(CodeActivityMetadata metadata)
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{
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// the creator of this activity is expected to have checked visibility of LocationReference.
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// we override the base CacheMetadata to avoid unnecessary reflection overhead.
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}
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protected sealed override Location<T> Execute(CodeActivityContext context)
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{
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try
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{
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context.AllowChainedEnvironmentAccess = true;
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return context.GetLocation<T>(this.LocationReference);
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}
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finally
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{
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context.AllowChainedEnvironmentAccess = false;
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}
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}
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ActivityWithResult ILocationReferenceExpression.CreateNewInstance(LocationReference locationReference)
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{
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return new EnvironmentLocationReference<T>(locationReference);
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}
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}
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}
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