Launching an application from WPF Window using Process Class

Question

I am using the Process to class to launch a program (notepad, for example) and wait for it to exit from a WPF window.  

When I drag notepad over my WPF window, the WPF Window does not repaint and its distorted.

What is the correct way to force a refresh, so that I never see parts of Notepad in my WPF window?

I've tried various options and timers but nothing seems to work consistly?

Answer 1

You don't want to call Process.Start from the UI thread and wait.  The UI thread will not update your UI while the thread is busy.  Register a callback with the Process class.

XAML
 

<StackPanel>
    <Button x:Name='ShowNotepad'
            Click='Button_Click' Content='Show Notepad'/>
  </StackPanel>

C# code

private void Button_Click(object sender, RoutedEventArgs e) {
	ProcessStartInfo startInfo = new ProcessStartInfo();
	startInfo.FileName = "Notepad.exe";
	Process process = Process.Start(startInfo);
	process.EnableRaisingEvents = true;
	process.Exited += ProcessDone;
}
public void ProcessDone(Object s, EventArgs e) {
	MessageBox.Show("Done");
	// note you will have to marshal back to UI thread
	// to access any UI elements
	Dispatcher.Invoke(new Action<string>(UpdateUI), "Finished");
}
public void UpdateUI(string message) {
	this.Title = message;
}

or VB code

Private Sub Button_Click(ByVal sender As Object, ByVal e As RoutedEventArgs)
	Dim startInfo As New ProcessStartInfo()
	startInfo.FileName = "Notepad.exe"
	Dim process As Process = Process.Start(startInfo)
	process.EnableRaisingEvents = True
	AddHandler process.Exited, AddressOf ProcessDone
End Sub
Public Sub ProcessDone(ByVal s As Object, ByVal e As EventArgs)
	MessageBox.Show("Done")
	' note you will have to marshal back to UI thread
	' to access any UI elements
	Dispatcher.Invoke(New Action(Of String)(AddressOf UpdateUI), "Finished")
End Sub
Public Sub UpdateUI(ByVal message As String)
	Me.Title = message
End Sub

---

Walt | http://wpfwonderland.wordpress.com

Answer 2

Thank you for taking the time to answer this.
This does resolve my refresh issue.

Next I'll consider
- the best way to disable controls( I may want to prevent the user from doing anything and suspend the WPF UI and wait until the call back). I don't want the user to be able to click the button while the launched program is still running.
- StandardOutput - to determine how the launched application terminated( ie: if the pressed OK or Cancel )