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Implement marker interface
f#web

I'm currently working on an F# web framework and starting small by setting it atop ASP.NET. I want to implement IRequiresSessionState, but that interface is just a marker and has no methods or properties:

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type MyHandler() =
  interface IRequiresSessionState
  interface IHttpHandler with
    member this.IsReusable = false
    member this.ProcessRequest(context) =
      // do something with the context

I get an error on IRequiresSessionState stating, "The type 'obj' is not an interface type." However, I also can't use with, as that requires I follow it up with an implementation, right? Is this possible?

.

Turns out that works just fine once you have the correct open statements.

By on 5/2/2010 2:50 PM ()

The syntax is right. I bet you haven't opened the namespace that contains IRequireSessionState. Here's an example that works (when referencing Microsoft.Build.Framework):

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type MyType() =
    interface Microsoft.Build.Framework.ITaskHost                
    interface System.IDisposable with
        member this.Dispose() = ()

If I just say "ITaskHost" (a marker interface) without opening the namespace, I get two errors, one of which is what you mentioned.

By on 5/2/2010 2:27 PM ()

Just figured that out. Thanks, Brian!

By on 5/2/2010 2:51 PM ()

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