Get text from another application

Question

I'd like to retrieve text from textbox in my another application. ProcessName from second application is 'TestTextBox', TextBox's name is 'textBox1'.

My code, which returns empty string:

[DllImport("user32.dll")]
static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, long wParam, [MarshalAs(UnmanagedType.LPStr)] StringBuilder lParam);

Process[] processes = Process.GetProcessesByName("TestTextBox");
foreach (Process p in processes)
{
    IntPtr pFoundWindow = p.MainWindowHandle;
    const int WM_GETTEXT = 0x0D;
    StringBuilder sb = new StringBuilder();
    IntPtr retVal = SendMessage(pFoundWindow, WM_GETTEXT, 100, sb);
    MessageBox.Show(sb.ToString());
}

Answer 1

What is the "another application"? Is it something you are writing? Could it be running on another machine? In another domain? Under another user account? Could the target application, form, or textbox ever change? Do you need asynchronous (i.e. non-blocking) communication between applications?

If the answer to any of those questions is "yes", you should consider using .Net Remoting. This is available from .Net 2.0.

Answer 2

In june there was a discussion of how to find the handle of a child control, perhaps this helps.