Generic InArgument throws an exception trying to get the value

Question

I have an Activity where I declared a InArgument without a type (because I want to know the type of the Expression at design time).

When I execute the activity I get this error in var contentTelegram line:

"The argument of type '<type>' cannot be used.  Make sure that it is declared on an activity."

Here is my code:

public InArgument Content { get; set; }


protected override PlcMessage Execute(CodeActivityContext context)
        {

            try
            {
                var contentTelegram = Content.Get(context); 

               return new PlcMessage();
            }
            catch (Exception ex)
            {

                throw;
            }


        }

Answer 1

这是我所做的：

工作流运行时需要了解参数中使用的类型，因此 CacheMetadata 是使其工作的关键，CacheMetadata 使用反射来了解参数，请注意，这只适用于简单的情况。

public sealed class MyActivity: CodeActivity
{
    private RuntimeArgument outMyRuntimeArgument;

    // Define an activity input argument of type string
    public OutArgument MyUntypedArgument { get; set; }


    protected override void CacheMetadata(CodeActivityMetadata metadata)
    {
        outMyArgument= new RuntimeArgument("MyUntypedArgument", MyUntypedArgument.ArgumentType, ArgumentDirection.Out);
        metadata.Bind(MyUntypedArgument, outArgument);
        metadata.AddArgument(outMyArgument);
    }     


    protected override void Execute(CodeActivityContext context)
    {
        context.SetValue(outMyRuntimeArgument, Activator.CreateInstance(Type));
    }
}