fsi event loop

在默认情况下fsi 中的Event loop是绑定到winform中的，如果我们在fsi中测试WPF的控件时，加载自定义的WPF控件，有些消息就无法正常响应。比如按键消息就无法正常响应。这时需要重定义fsi的Event loop。好在有现成的示例。

module WPFEventLoop =     
    open System    
    open System.Windows    
    open System.Windows.Threading    
    open Microsoft.FSharp.Compiler.Interactive    
    open Microsoft.FSharp.Compiler.Interactive.Settings    

    type RunDelegate<'b> = delegate of unit -> 'b     
    let Create() =         
        let app  =             
            try                 
                // Ensure the current application exists. This may fail, if it already does.                
                let app = new Application() in                 
                // Create a dummy window to act as the main window for the application.                
                // Because we're in FSI we never want to clean this up.                
                new Window() |> ignore;                 
                app              
            with :? InvalidOperationException -> Application.Current        
        let disp = app.Dispatcher        
        let restart = ref false        
        { new IEventLoop with             
            member x.Run() =                    
                app.Run() |> ignore                 
                !restart             

            member x.Invoke(f) =                  
                try
                    disp.Invoke(DispatcherPriority.Send,new RunDelegate<_>(fun () -> box(f ()))) |> unbox                 
                with e -> eprintf "\n\n ERROR: %O\n" e; reraise()             

            member x.ScheduleRestart() =   ()                 
            //restart := true;                 
            //app.Shutdown()        
         }     

    let Install() = fsi.EventLoop <-  Create()

WPFEventLoop.Install()

运行之后按键消息就可以正常响应了。