How to write state machines with c#?

Question

I need to write state machines that run fast in c#. I like the Windows Workflow Foundation library, but it's too slow and over crowded with features (i.e. heavy). I need something faster, ideally with a graphical utility to design the diagrams, and then spit out c# code. Any suggestions? Thanks!

Solution 1

Ultimately, you probably want the newly redesigned WF engine in .NET 4.0, as it is much faster and provides a flowchart activity (not quite a state machine, but works for most scenarios) and a nice designer UI experience. But since it's not yet released, that is probably not a good answer for now.

As an alternative, you could try stateless, a library specifically for creating state machine programs in .NET. It doesn't appear to provide a UI, but looks well-suited to fulfill your other goals.

Solution 2

Yeah, Microsoft may have been ahead of their time with State Machine WF. Sequential Workflows are being received much better.

When we decided on using a state machine, we rolled our own. because we couldn't find an acceptable framework with a UI. Here are our steps. Hope they'll help you.

1. Create your state interface:

   public interface IApplicationState
   {
       void ClickOnAddFindings();        
       void ClickOnViewReport();
       //And so forth
   }
   

2. Create the states and have them implement the interface:

   public class AddFindingsState : IApplicationState
   {
       frmMain _mForm;
   
       public AddFindingsState(frmMain mForm)
       {
           this._mForm = mForm;
       }
   
       public void ClickOnAddFindings()
       {            
       }
   
       public void ClickOnViewReport()
       {
           // Set the State
           _mForm.SetState(_mForm.GetViewTheReportState());
       }
   }
   

3. Instantiate the states in your main class.

   IApplicationState _addFindingsState;
   IApplicationState _viewTheReportState;
   _addFindingsState = new AddFindingsState(this);
   _viewTheReportState = new ViewTheReportState(this);
   

4. When the user does something requiring a change of state, call the methods to set the state:

   _state.ClickOnAFinding();
   

Of course, the actions will live in the particular instance of the IApplicationState.

Comments

[Nestor]

Interesting implementation. Thanks for sharing.

[Jonathan Oliver]

+1 for stateless. It's a great little library and a breath of fresh air compared to Workflow Foundation (even WF 4.0).