Sequence with CodeActivities with WorkflowInvoker's input arguments doesn't work? - workflow-foundation-4

Question

Why is it not possible to pass the arguments to CodeActivity via WorkflowInvoker's input dictionary, if the activities are within a Sequence? The WorkflowInvoker.Invoke(sequence, dict) method throws the following exception:
Additional information: The values provided for the root activity's arguments did not satisfy the root activity's requirements:
'Sequence': The following keys from the input dictionary do not map to arguments and must be removed: Arg. Please note that argument names are case sensitive.
class Program
{
static void Main(string[] args)
{
var sequence = new Sequence();
var start = new Start();
var end = new End();
sequence.Activities.Add(start);
sequence.Activities.Add(end);
var dict = new Dictionary();
dict["Arg"] = "Debug text.";
WorkflowInvoker.Invoke(sequence, dict);
}
}
public class Start : CodeActivity
{
public InArgument Arg { get; set; }
protected override void Execute(CodeActivityContext context)
{
Debug.WriteLine(Arg.Get(context));
}
}
public class End : CodeActivity
{
public InArgument Arg { get; set; }
protected override void Execute(CodeActivityContext context)
{
Debug.WriteLine(Arg.Get(context));
}
}
// ************** Second example with custom sequence *************************
class Program
{
static void Main(string[] args)
{
var seq = new MySequence();
seq.Activities.Add(new Last());
seq.Activities.Add(new First());
var dict = new Dictionary();
dict["Arg"] = "Text";
WorkflowInvoker.Invoke(seq, dict);
}
}
public class First : CodeActivity
{
public InArgument Arg { get; set; }
protected override void Execute(CodeActivityContext context)
{
var val = Arg.Get(context);
}
}
public class Last : CodeActivity
{
public InArgument Arg { get; set; }
protected override void Execute(CodeActivityContext context)
{
var val = Arg.Get(context);
}
}
public class MySequence : NativeActivity
{
public InArgument Arg { get; set; }
public Collection Activities = new Collection();
protected override void CacheMetadata(NativeActivityMetadata metadata)
{
base.CacheMetadata(metadata);
metadata.SetChildrenCollection(Activities);
}
protected override void Execute(NativeActivityContext context)
{
foreach (var activity in Activities)
context.ScheduleActivity(activity);
}
}

Answer 1

The code activities take their arguments from the container they are in not the input dictionary. The container needs to have an in argument matching the one in the dictionary.
Sequences don't accept arguments so you wrap them in an Activity.
An Activity constructed as below is a worklfow
public class MyCodeWorkflow : Activity
{
public InArgument<string> inMSG { get; set; }
public OutArgument<string> outMSG { get; set; }
public MyCodeWorkflow()
{
this.Implementation = () => new Sequence {
Activities =
{
new WriteLine
{
Text=new InArgument<string>((activityContext)=>this.inMSG.Get(activityContext))
},
new Assign<string>
{
To=new ArgumentReference<string>("outMSG"),
Value=new InArgument<string>
(
(activityContext)=>this.inMSG.Get(activityContext)
)
}
}
};
}
}
//host
static void Main(string[] args)
{
IDictionary<string, object> input = new Dictionary<string, object>();
input.Add("inMSG","hello");
IDictionary<string, object> output = new Dictionary<string, object>();
MyCodeWorkflow activity = new MyCodeWorkflow();
output = WorkflowInvoker.Invoke(activity,input);
Console.WriteLine(output["outMSG"]);
}
The code above was taken from http://xhinker.com/post/WF4Authoring-WF4-using-imperative-code%28II%29.aspx