Assorted Windows Workflow Foundation

My name is Tom Lake. I previously worked on the Windows Workflow Foundation Activities test team and created these blog posts and samples to help before the official samples were available.

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  • Blog Post: Are you getting a "The root activity type is invalid" error with the Custom Activity Designer sample?

    Several peolple have gotten a "The root activity type is invalid" error when using the Custom Activity Designer sample that can be found at http://wf.netfx3.com/files/folders/activity_behavior/entry840.aspx . I created an update project that should resolve the problem, which can be downloaded from the...
  • Blog Post: How to use custom ActivityCondition or filter which ActivityConditions are available

    If you have your own custom ActivityCondition you are only going to be able to use it with your custom activities, not out of the box activities like While or IfElseBranch. First start by creating your custom ActivityCondition like the following: [ DisplayName ( "Custom Activity Condition" )] ...
  • Blog Post: Switch activity

    The Switch activity I created is based on the switch statement in C# or the Select Case statements in VB . You have an expression and one or more case statements, one of which can be the default. To model within workflow the case becomes a property that must be on the children of the Switch activity...
  • Blog Post: Basics of Working with Custom Types in Workflow

    If you have used a custom type for an activity / workflow property you have probably ran into a few issues. You might have had problems trying to get it serialized correctly or to be able to set the value in the property browser. With this post I will try and shed some light on some of the basics. I...
  • Blog Post: Do you want to invoke another workflow but you won't know which one until runtime?

    The InvokeWorkflowActivity that ships with WF requires you to set the type of the target workflow at design time. If you won’t know which workflow to invoke until runtime you need to write a custom activity. To invoke a workflow need to use the IStartWorkflow service that you can get from the ActivityExecutionContext...
  • Blog Post: Do you need to launch another process from your workflow?

    When start another process from your workflow you can’t just not return from the Execute method until the process completes. This would block the entire workflow from receiving any other events and would hold onto the thread. Instead you need to use a queue to get notification when the process completes...
  • Blog Post: How to set activity property from a custom input form

    Sometime you might want to create an input form for your user to set properties on your custom activity. Unfortunately when you set the properties directly on the activity from the input form the values don’t always get reflected on your activity. To resolve this you need to set the value on the PropertyDescriptor...
  • Blog Post: Couple of custom activities that you can use to synchronize branches of a ParallelActivity

    You could use a SynchronizationScope Activity, but this would block execution all together in the other branches since the thread is locked until the activity is done executing. If that is not the behavior you are looking for here are two options. First, WaitFor, will block the branch that it is in until...
  • Blog Post: Have you had problems using the FileWatcher sample in a StateMachineWorkflow or WhileActivity?

    If you have tried to use the FileWatcherActivity in either a WhileActivity or a StateMachineWorkflow you have probably not had much luck. The changes need to be made to the base activity InputActivity. To get it working in a while activity you need the following change to the ProcessQueueItem method...
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