How to get the window from the Process in WPF?

Question

I have an application (A) in WPF. I launched another application (B) from the first application (A). I need to get the window of application (B).

I tried with "Process" to get the window of application (B), I can get the windowHandle by using the Process, but when I tried to get this as a window it returns null.

The application (B) is launched by using the Process.Start();. Below I have attached the code snippet.

Please suggest how to get the window of application (B) from the Process or any other solution.

I tried like this in c#.

window = new Window();
window.Show();

ProcessStartInfo processInfo = new ProcessStartInfo();
processInfo.FileName = "D:\Samples\ButtonSample\bin\Debug\ButtonSample.exe";
processInfo.ErrorDialog = true;
processInfo.UseShellExecute = false;
processInfo.RedirectStandardOutput = true;

Process proc = Process.Start(processInfo); // Here the application(B) is launched

string fileName = Path.GetFileNameWithoutExtension("D:\Samples\ButtonSample\bin\Debug\ButtonSample.exe");
Process[] p = Process.GetProcessesByName(fileName);
IntPtr handle = p[0].MainWindowHandle;
Window window = HwndSource.FromHwnd(handle)?.RootVisual as Window;

Answer 1

HwndSource.FromHwnd is for the current process

What are you trying to do ?

(the Win32 handle can be sufficient or UI Automation to manipulate XAML controls)

Answer 2

Hi,@SaranRaj Chandrasekaran. Is there an update for this question? Did the following code help you?

 <StackPanel>
        <TextBlock Text="a"/>
        <Button Click="Button_Click" Content="open" Height="50"/>
    </StackPanel>

Codebedhind:

  public partial class MainWindow : Window
    {
      
        public MainWindow()
        {
            InitializeComponent();
           

        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            ProcessStartInfo processInfo = new ProcessStartInfo();
            processInfo.FileName = "C:\\...\\WpfAppB.exe";
            processInfo.ErrorDialog = true;
            processInfo.UseShellExecute = false;
            processInfo.RedirectStandardOutput = true;

            Process processB = Process.Start(processInfo);
            if (processB != null)
            {
                IntPtr mainWindowHandle = processB.MainWindowHandle;

                User32.Rect windowRect = new User32.Rect();
                User32.GetWindowRect(mainWindowHandle, ref windowRect);

                Point mousePosition = Mouse.GetPosition(null);

                double screenWidth = SystemParameters.PrimaryScreenWidth;
                double screenHeight = SystemParameters.PrimaryScreenHeight;

                double x = windowRect.Left + mousePosition.X - screenWidth;
                double y = windowRect.Top + mousePosition.Y - screenHeight;
                MessageBox.Show("location"+ x + y);
            }

        }
    }
    public static class User32
    {
        [DllImport("User32.dll")]
        public static extern bool GetWindowRect(IntPtr hwnd, ref Rect rectangle);

        [StructLayout(LayoutKind.Sequential)]
        public struct Rect
        {
            public int Left;
            public int Top;
            public int Right;
            public int Bottom;
        }
    }

ApplicationB:

 <Grid>
        <TextBlock Text="b"/>
    </Grid>

The result:

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