Win32, getting a window title from a hWnd

Question

If I use EnumWindows to get all windows, how would i use a hWnd to find the title of a window (so as to differentiate between windows so an action is performed to only windows with a certain title)?

Thanks in advance,
- Javawag

Answer 1

PInvoke GetWindowText

Answer 2

Sounds about right, but it didn't work. This is the code I used:

Code Snippet - GetWindowText

[DllImport("User32.dll")]
public static extern string GetWindowText(int hWnd);

and I get an "Attempted to read or write protected memory. This is often an indication that other memory is corrupt." error. Any ideas?

- Javawag

Answer 3

Try

Code Snippet

[DllImport("user32.dll", CharSet=CharSet.Auto)]
public static extern int GetWindowText(HandleRef hWnd, StringBuilder lpString, int nMaxCount);

 

Answer 4

You'll probably want to use that in  conjunction with GetWindowTextLength:

Code Snippet

[DllImport("user32.dll", CharSet=CharSet.Auto)]
public static extern int GetWindowTextLength(HandleRef hWnd);
[DllImport("user32.dll", CharSet=CharSet.Auto)]
public static extern int GetWindowText(HandleRef hWnd, StringBuilder lpString, int nMaxCount);
 
//...
            int capacity = GetWindowTextLength(new HandleRef(this, handle)) * 2;
            StringBuilder stringBuilder = new StringBuilder(capacity);
     GetWindowText(new HandleRef(this, handle), stringBuilder, stringBuilder.Capacity);

 

If all you want is the name window text of all processes, you can use Process.GetProcesses() the use Process.MainWindowTitle; but MainWindowTitle will not get the latest window text (just the text the first time it is called on a process).

Answer 5

Ok, this looks promising! However, I really don't know how to use StringBuilders... could you show me what I'd need to do if i put my code here?:

frmMain.cs: (this part is repeated for every open window, using each one's hWnd)
if (Win32.GetWindowText(hWnd) == "Untitled - Notepad")
{

Win32.SendMessage(hWnd, Win32.WM_SYSCOMMAND, Win32.SC_RESTORE, 0);

}

Win32.cs:
public const int SC_MINIMIZE = 0xF020;
[DllImport("User32.dll")]
public static extern int EnumWindows(EnumWindowsProc cb, int lparam);
public delegate bool EnumWindowsProc(int hWnd, int lParam);
[DllImport("User32.dll")]
public static extern int GetWindowText(HandleRef hWnd, StringBuilder lpString, int nMaxCount);

What code would I need to use in frmMain.cs to get the name of a single form from its hWnd and check it against my test string (which, at the moment, is "Untitled - Notepad")?

Ok, I fiddled around, and the original suggestion worked. I'll mark that as the answer. Thanks a lot!!
- Javawag