wf4 An activity can only access its own implementation variables

问题

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);
    }

resulting in

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.

I attempted to expose them via cachemetadata

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

And that results in

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

My variables are c# expressions and compiled with

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

回答1:

I was able to hack around it with

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

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

回答2:

I think if you are inside a while loop with a counter in the middle and trying to access a variable like "Number" + i.ToString you will not get the correct answer. It will not evaluate that 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)); 
    }
 }

You will need to add that RuntimeArgument to the ArgumentCollection as shown above.

I got this from my answered question : While activity in WF 4 rehosted designer

来源：https://stackoverflow.com/questions/30616844/wf4-an-activity-can-only-access-its-own-implementation-variables

标签

workflow-foundation-4