Most of the time in software when we say “Parallel” we mean that multiple threads are being used to do work concurrently.  Because of this, many customers ask if the Parallel activity works this way in Windows Workflow Foundation.  I know there is a great deal of confusion about activities and threads and in the next few posts I hope to bring some clarity. Activity Lifecycle Phase 1: Scheduling Activities are scheduled by a parent activity (or the Workflow Runtime if they are the root activity...

If you are a C# developer using Workflow you might not know how VB does type conversion. Imagine this simple example.  I’ve got some classes which use inheritance 1: public abstract class Shape 2: { 3: public int Top { get; set; } 4:   5: public int Left { get; set; } 6: } 7:   8: public class Circle : Shape 9: { 10: public int Radius { get; set; } 11: } 12:   13: public class Square : Shape 14: { 15: public int Length { get; set; } 16:   17: public int Width { get; set;...

If you want to read the AppFabric Monitoring Database from a Web Application your web app will have to have permission to login. If you try to run a web app that does not have permission you will likely see this Cannot open database "AppFabricMonitoringDB" requested by the login. The login failed. Login failed for user 'IIS APPPOOL\DefaultAppPool'. You have two choices. Run the Web Application in an AppPool using an identity that has permission to login Grant permissions to the...

I can’t count how many times this has bitten me…  You create a new Workflow Service.  You create a client app, add a service reference and boom! There is no context attached to the incoming message for the service and the current operation is not marked with "CanCreateInstance = true". In order to communicate with this service check whether the incoming binding supports the context protocol and has a valid context initialized. For some strange reason, our default Workflow Service...

A question on StackOverflow about scheduling child activities with some additional input parameters made me remember that this is kind on not obvious to figure out and even though I new the answer I had to think hard before I could code up a demo. So I figured I might as well post it on my blog for future reference.   The problem is that activities are normally just scheduled and their inputs and outputs are configured using Visual Basic expressions. Most of the time that is just fine and does...