Databases
StackOverflow2013
Postsdbo
POHow do I get a System.Windows.Form instance from its Win32 handle?
Body
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POHow do I get a System.Windows.Form instance from its Win32 handle?
    text
    copied!<p>The following code implements a simple singleton that ensures only 1 instance of my application can be run. However, if another instance is started, I need to be able to grab that instance's command-line arguments, pass them to the initial instance, then terminate the second instance.</p> <p>The issue comes in when I'm attempting to get hold of the first instance of the application. Once I've found the handle of that instance's main form, I pass it to the <code>Control.FromHandle()</code> method, expecting to get back a <code>MainForm</code>. Instead, the return value is always <code>null</code>. (<code>Control.FromChildHandle()</code> gives the same result.)</p> <p>Therefore, my question is simply: what am I doing wrong? And is this even possible in .NET?</p> <pre><code>public class MainForm : Form { [DllImport("user32")] extern static int ShowWindowAsync(IntPtr hWnd, int nCmdShow); [DllImport("user32")] extern static bool SetForegroundWindow(IntPtr hWnd); private Mutex singletonMutex; private void MainForm_Load(object sender, EventArgs e) { bool wasCreated; singletonMutex = new Mutex(false, Application.ProductName + "Mutex", out wasCreated); // returns false for every instance except the first if (!wasCreated) { Process thisProcess = Process.GetCurrentProcess(); Process[] peerProcesses = Process.GetProcessesByName(thisProcess.ProcessName.Replace(".vshost", string.Empty)); foreach (Process currentProcess in peerProcesses) { if (currentProcess.Handle != thisProcess.Handle) { ShowWindowAsync(currentProcess.MainWindowHandle, 1); // SW_NORMAL SetForegroundWindow(currentProcess.MainWindowHandle); // always returns null !!! MainForm runningForm = (MainForm) Control.FromHandle(currentProcess.MainWindowHandle); if (runningForm != null) { runningForm.Arguments = this.Arguments; runningForm.ProcessArguments(); } break; } } Application.Exit(); return; } } </code></pre>
 

Querying!

 
Guidance
An individual column

Larger individual text columns get their own page to allow for proper reading.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload