Workflow foundation custom Assign Activity - workflow-foundation-4

Question

I am defining this in my designer:
<sap:WorkflowItemPresenter>
<statements:Assign DisplayName="Assign"/>
</sap:WorkflowItemPresenter>
I thought it would simply work if i add the Assign there but i was wrong.
[Browsable(false)]
public Activity Body { get; set; }
protected override void Execute(NativeActivityContext context)
{
ActivityInstance res = context.ScheduleActivity(Body, new CompletionCallback(OnExecuteComplete));
}
/// <summary>
/// Called from Execute when Condition evaluates to true.
/// </summary>
/// <param name="context">The context.</param>
/// <param name="instance">The instance.</param>
public void OnExecuteComplete(NativeActivityContext context, ActivityInstance instance)
{
//to be added
}
This is the code from the base class.
I don't need to alter the Assign activity at all, i just want to get access to the NativeActivityContext. In fact i am trying to wrap it up and do some checks on the context's properties in the OnExecuteComplete method. Is there a way to accomplish this?
EDIT 1:
DotNetHitMan suggested and shown me on WF 4 Rehosted Designer - get foreach InArgument Value how to work with those trackings and i indeed succeeded to work this out with his solution:
if (trackingEventArgs.Activity is Assign)
{
Assign ass = trackingEventArgs.Activity as Assign;
if (ass.To.Expression != null)
{
dynamic vbr = null;
if ((ass.To.Expression is VisualBasicReference<int>))
{
//vbr.ExpressionText will hold the value set in the To section of the Assign activity, one of the variables will reside here
vbr = ass.To.Expression as VisualBasicReference<int>;
}
else if ((ass.To.Expression is VisualBasicReference<string>))
{
vbr = ass.To.Expression as VisualBasicReference<string>;
}
ActivityStateRecord activityStateRecord = null;
if (trackingEventArgs.Record != null)
activityStateRecord = trackingEventArgs.Record as ActivityStateRecord;
if (activityStateRecord != null)
{
if (activityStateRecord.Arguments.Count > 0)
{
//checking if the variable defined in the To section is to be displayed in the watch window
GlobalFunctions.WatchWindowViewModel.VariableDefinition existingVariable = GlobalFunctions.WatchWindowViewModel.Instance.VariableExists(vbr.ExpressionText);
if (existingVariable != null)
{
foreach (KeyValuePair<string, object> argument in activityStateRecord.Arguments)
{
if (argument.Key.Equals("Value"))
{
Application.Current.Dispatcher.Invoke(
() =>
{
existingVariable.VariableValue.Clear();
existingVariable.VariableValue.Add(
argument.Value.ToString());
});
}
}
}
}
}
}
}
I still face something a bit ugly. When checking the arguments for the Assign activity i get the key "Value". But if i define a variable named "i" and want to see its changes as this Assign executes i have to take a look at that VisualBasicReference<> to check the name of the variable declared there just like in the code above. This way of doing it works indeed and i managed to cover ints and strings which is fine for now .. but is there any shortcut that can be used in my code ?
EDIT 2
I got a new idea today and put it to work:
Here is the library code:
public sealed class CustomAssign : NativeActivity, IActivityTemplateFactory
{
[Browsable(false)]
public Activity Body { get; set; }
protected override void Execute(NativeActivityContext context)
{
ActivityInstance res = context.ScheduleActivity(Body, new CompletionCallback(OnExecuteComplete));
}
/// <summary>
/// Called from Execute when Condition evaluates to true.
/// </summary>
/// <param name="context">The context.</param>
/// <param name="instance">The instance.</param>
public void OnExecuteComplete(NativeActivityContext context, ActivityInstance instance)
{
//to be added
}
Activity IActivityTemplateFactory.Create(System.Windows.DependencyObject target)
{
return new CustomAssign
{
Body = new Assign()
};
}
}
And the designer:
<sap:ActivityDesigner x:Class="ARIASquibLibrary.Design.CustomAsignDesigner"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:sap="clr-namespace:System.Activities.Presentation;assembly=System.Activities.Presentation"
xmlns:sapv="clr-namespace:System.Activities.Presentation.View;assembly=System.Activities.Presentation"
xmlns:statements="http://schemas.microsoft.com/netfx/2009/xaml/activities" Collapsible="False" BorderThickness="20" BorderBrush="Transparent">
<sap:ActivityDesigner.Template>
<ControlTemplate TargetType="sap:ActivityDesigner">
<Grid>
<ContentPresenter HorizontalAlignment="Center"
VerticalAlignment="Center"/>
</Grid>
</ControlTemplate>
</sap:ActivityDesigner.Template>
<DockPanel LastChildFill="True">
<sap:WorkflowItemPresenter Item="{Binding Path=ModelItem.Body, Mode=TwoWay}"/>
</DockPanel>
</sap:ActivityDesigner>
So, in a few words: i've hosted the Assign activity in my custom activity and changed the ControlTemplate in order to keep only the ContentPresenter, which in turn will be the Assign. Now, by dragging it to the designer, you will have exactly the original appearance but with the ability to write code and check the execution steps in the :
protected override void Execute(NativeActivityContext context)
or
public void OnExecuteComplete(NativeActivityContext context, ActivityInstance instance)
Why is that? Through the context.DataContext you can get to all the variables and arguments in the scope where this activity resides in order to develop a watch window.

Answer 1

Rather than dealing with each variable type just convert the expression to its base interface.
ITextExpression vbr = ass.To.Expression as ITextExpression;
You can then just access the expression text property without caring about the type of variable assigned to the expression.
GlobalFunctions.WatchWindowViewModel.VariableDefinition existingVariable = GlobalFunctions.WatchWindowViewModel.Instance.VariableExists(vbr.ExpressionText);
This should cater for (I hope) all variable types that can be applied.