wf4 一个activity只能访问自己的实现变量

Question

我有一个带有变量（C# 表达式）的 activity，但无法读取它们的值。

    public Collection<Variable> Variables { get; } = new Collection<Variable>();

    protected override void DoExecute(NativeActivityContext context)
    {
        var x = Variables.FirstOrDefault(...).Get(context);
    }

导致

Activity '1.1: MyActivity' cannot access this variable 
because it is declared at the scope of activity '1.1: MyActivity'.  
An activity can only access its own implementation variables.

我试图通过缓存元数据公开它们

    protected override void CacheMetadata(NativeActivityMetadata metadata)
    {
        metadata.SetImplementationVariablesCollection(Variables);
    }

结果是

Exception <System.NotSupportedException: 
Expression Activity type 'CSharpValue`1' requires compilation in order to run.  
Please ensure that the workflow has been compiled.

我的变量是 c# 表达式并使用

编译

var wwfActivity = ActivityXamlServices.Load(xamlReader, new ActivityXamlServicesSettings {CompileExpressions = true});

Answer 1

我可以用

破解它

var var = context.DataContext.GetProperties()["variableName"];
var value = var.GetValue(context.DataContext) as Whatever;

没有覆盖CacheMetadata方法，但感觉有点奇怪；

Answer 2

我认为如果你在中间有一个计数器的 while 循环中并试图访问像 "Number" + i.ToString 这样的变量，你将不会得到正确的答案。它不会评估 i.ToString.

using System; 
using System.ComponentModel; 
using System.IO;
using System.Runtime; 
using System.Activities.Validation;
using System.Collections.Generic;
using System.Windows.Markup;
using System.Collections.ObjectModel;
using System.Activities; 

namespace WorkflowConsoleApplication2
{

public sealed class CodeActivity1 : CodeActivity
{
    // Define an activity input argument of type string
    [DefaultValue(null)]
    public InArgument<string> Test
    {
        get;
        set;
    }

    protected override void CacheMetadata(CodeActivityMetadata metadata)
    {
        RuntimeArgument textArgument = new RuntimeArgument("Test",    typeof(string), ArgumentDirection.In);
        metadata.Bind(this.Test, textArgument);


        metadata.SetArgumentsCollection(
        new Collection<RuntimeArgument> 
        {
            textArgument,
        });
    }

    // If your activity returns a value, derive from CodeActivity<TResult>
    // and return the value from the Execute method.
    protected override void Execute(CodeActivityContext context)
    {
        Console.WriteLine(this.Test.Get(context)); 
    }
 }

您需要将该 RuntimeArgument 添加到 ArgumentCollection 中，如上所示。

我从我回答的问题中得到这个：

wf4 一个activity只能访问自己的实现变量

wf4 An activity can only access its own implementation variables

c#

workflow-foundation-4