wf4 一个活动只能访问自己的实现变量 [英] wf4 An activity can only access its own implementation variables

问题描述

我有一个带有变量(C# 表达式)的活动，但无法读取它们的值.

I have an activity with variables (which are C# expressions), but not able to read their values.

    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

I attempted to expose them via cachemetadata

    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# 表达式并用

My variables are c# expressions and compiled with

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

推荐答案

我能够用

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；

without overriding the CacheMetadata method, but it feels a lil weird;

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