|
//-----------------------------------------------------------------------------
// Copyright (c) Microsoft Corporation. All rights reserved.
//-----------------------------------------------------------------------------
namespace System.Activities.Expressions
{
using System;
using System.Activities.ExpressionParser;
using System.Activities.XamlIntegration;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq.Expressions;
using System.Runtime;
using System.Windows.Markup;
// consciously not XAML-friendly since Linq Expressions aren't create-set-use
[Fx.Tag.XamlVisible(false)]
[DebuggerStepThrough]
public sealed class LambdaReference<T> : CodeActivity<Location<T>>, IExpressionContainer, IValueSerializableExpression
{
Expression<Func<ActivityContext, T>> locationExpression;
Expression<Func<ActivityContext, T>> rewrittenTree;
LocationFactory<T> locationFactory;
public LambdaReference(Expression<Func<ActivityContext, T>> locationExpression)
{
if (locationExpression == null)
{
throw FxTrace.Exception.ArgumentNull("locationExpression");
}
this.locationExpression = locationExpression;
this.UseOldFastPath = true;
}
// this is called via reflection from Microsoft.CDF.Test.ExpressionUtilities.Activities.ActivityUtilities.ReplaceLambdaValuesInActivityTree
internal Expression LambdaExpression
{
get
{
return this.locationExpression;
}
}
protected override void CacheMetadata(CodeActivityMetadata metadata)
{
CodeActivityPublicEnvironmentAccessor publicAccessor = CodeActivityPublicEnvironmentAccessor.Create(metadata);
// We need to rewrite the tree.
Expression newTree;
if (ExpressionUtilities.TryRewriteLambdaExpression(this.locationExpression, out newTree, publicAccessor, true))
{
this.rewrittenTree = (Expression<Func<ActivityContext, T>>)newTree;
}
else
{
this.rewrittenTree = this.locationExpression;
}
// inspect the expressionTree to see if it is a valid location expression(L-value)
string extraErrorMessage = null;
if (!ExpressionUtilities.IsLocation(this.rewrittenTree, typeof(T), out extraErrorMessage))
{
string errorMessage = SR.InvalidLValueExpression;
if (extraErrorMessage != null)
{
errorMessage += ":" + extraErrorMessage;
}
metadata.AddValidationError(errorMessage);
}
}
protected override Location<T> Execute(CodeActivityContext context)
{
if (this.locationFactory == null)
{
this.locationFactory = ExpressionUtilities.CreateLocationFactory<T>(this.rewrittenTree);
}
return this.locationFactory.CreateLocation(context);
}
public bool CanConvertToString(IValueSerializerContext context)
{
return true;
}
public string ConvertToString(IValueSerializerContext context)
{
// This workflow contains lambda expressions specified in code.
// These expressions are not XAML serializable.
// In order to make your workflow XAML-serializable,
// use either VisualBasicValue/Reference or ExpressionServices.Convert
// This will convert your lambda expressions into expression activities.
throw FxTrace.Exception.AsError(new LambdaSerializationException());
}
}
}
|