gistfile1.txt

type LogicalCallContextEvent<'T>() = 
  let id = Guid.NewGuid()

  member this.Publish = this :> IDelegateEvent<Handler<'T>>
  member this.Trigger(arg:'T) =
    if CallContext.LogicalGetData(id.ToString()) <> null then
      (CallContext.LogicalGetData(id.ToString()) :?> Handler<'T>).Invoke(this, arg)

  interface IDelegateEvent<Handler<'T>> with

    member this.AddHandler(handler : Handler<'T>) = 
        CallContext.LogicalSetData(id.ToString(), Delegate.Combine(CallContext.LogicalGetData(id.ToString()) :?> Handler<'T>, handler) :?> Handler<'T>)

    member this.RemoveHandler(handler: Handler<'T>) = 
        CallContext.LogicalSetData(id.ToString(), Delegate.Remove(CallContext.LogicalGetData(id.ToString()) :?> Handler<'T>, handler) :?> Handler<'T>)