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Launch multiple WPF windows from fsi
f#wpf

Hi,

I have been trying quickly set up some visualisation capability from fsi using WPF controls. The intention is to define a discrimated union representing the data to display and then associate a pretty-printer to render this using WPF controls:

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type Plot = 
    | Data of seq<float*float>
    
let display_plot (plot: Plot) = 
    let thread = 
        new System.Threading.Thread(
            new System.Threading.ThreadStart( 
                fun () ->
                    // logic to render the plot would go here
                    new System.Windows.Window()
                    |> (Application()).Run
                    |> ignore                                           
                   )
        )
    thread.SetApartmentState(System.Threading.ApartmentState.STA)        
    thread.IsBackground <- true
    thread.Start()
    "plot"
                                    
fsi.AddPrinter(display_plot)

I then defined the following plots: 

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let p = Data (seq [for i in 0..360 -> let i' = (System.Math.PI / 180.) * float i in (i', sin i')])
let p2 = Data (seq [for i in 0..360 ->let i' = (System.Math.PI / 180.) * float i  in (i', cos i')])

When evaluating the first, 'p', in fsi a wpf window is launched correctly. However, when I evaluated 'p2' I get the following message:

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Unhandled Exception: System.InvalidOperationException: Cannot create more than one System.Windows.Application instance in the same AppDomain.
   at System.Windows.Application..ctor()
   at <A href="mailto:FSI_0008.clo@153.Invoke">FSI_0008.clo@153.Invoke</A>() in C:\Users\Micky\Documents\Visual Studio 2008\Projects\ConsoleApplication1\ConsoleApplication1\Program.fs:line 155
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

I realise this is a threading issue and wondered if someone could point me in the direction of some resources to establish the correct approach?

Regards,

Michael

.

To answer my own question...

I just came across this article:

[link:eprystupa.wordpress.com]

Lifting the code from there seems to work:

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let display_plot (plot: Plot) = 
    let thread = new System.Threading.Thread (
                        new System.Threading.ThreadStart( fun () ->
                                                                let window = new System.Windows.Window()
                                                                window.Show() |> ignore  
                                                                window.Closed.Add(fun _  -> window.Dispatcher.InvokeShutdown())
                                                                System.Windows.Threading.Dispatcher.Run()
                        )
                    )
    thread.SetApartmentState(System.Threading.ApartmentState.STA)
    thread.IsBackground <- true
    thread.Start()
    "plot"

Regards,

Michael

By on 5/11/2009 1:55 AM ()

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