C# How To Use WM_GETTEXT / GetWindowText API / Window Title

Answer :

public class GetTextTestClass{      [System.Runtime.InteropServices.DllImport("user32.dll", EntryPoint = "SendMessage", CharSet = System.Runtime.InteropServices.CharSet.Auto)]     public static extern bool SendMessage(IntPtr hWnd, uint Msg, int wParam, StringBuilder lParam);      [System.Runtime.InteropServices.DllImport("user32.dll", SetLastError = true)]     public static extern IntPtr SendMessage(int hWnd, int Msg, int wparam, int lparam);      const int WM_GETTEXT       = 0x000D;     const int WM_GETTEXTLENGTH = 0x000E;      public string GetControlText(IntPtr hWnd){          // Get the size of the string required to hold the window title (including trailing null.)          Int32 titleSize = SendMessage((int)hWnd, WM_GETTEXTLENGTH, 0, 0).ToInt32();          // If titleSize is 0, there is no title so return an empty string (or null)         if (titleSize == 0)             return String.Empty;          StringBuilder title = new StringBuilder(titleSize + 1);          SendMessage(hWnd, (int)WM_GETTEXT, title.Capacity, title);          return title.ToString();     } } 

GetWindowText won't give you the content of edit windows from other applications - it only supports default-managed text [like the captions of labels] across processes to prevent hangs... you'll have to send WM_GETTEXT.

You'll need to use a StringBuilder version of SendMessage:

[DllImport("user32.dll", CharSet = CharSet.Auto)] static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, [Out] StringBuilder lParam);  const int WM_GETTEXT = 0xD; StringBuilder sb = new StringBuilder(65535); // needs to be big enough for the whole text SendMessage(hWnd_of_Notepad_Editor, WM_GETTEXT, sb.Length, sb); 

Have a look at http://pinvoke.net/default.aspx/user32/GetWindowText.html and also the documentation on MSDN. Below you find a short code example how to use the GetWindowText method.