Using ::SendMessage in C#

[Andreas Philipson]

I need to get the following code working in C#:

char szText[255];
::SendMessage(hwndCurr, WM_GETTEXT, 255, (LPARAM)szText);
m_strPassword = szText;

And I've defined the SendMessage function

const int WM_GETTEXT = 0x000D;

[DllImport("user32.dll")]
static extern int SendMessage(IntPtr window, int message, int wparam, [Out]long lparam);

Does anybody know what I should do to make this work? Andreas Philipson

[Heath Stewart]

Define it like so:

const int WM_GETTEXT = 0x000D;
[DllImport("user32.dll", CharSet=CharSet.Ansi)]
static extern int SendMessage(IntPtr hWnd, int msg, int wParam, out char[] lParam);

You can get the HWND from controls' Handle property (and remember that Form derives from Control, so it has a handle too). Notice that I also used the out keyword (not the OutAttribute, which you could still use). This is necessary to get this to work in .NET. Call it like so:

char[] text = new char[255];
SendMessage(myTextBox.Handle, WM_GETTEXT, 255, out text);
password = text;

Now, if you're some cracker trying to get a password from another application, keep in mind that calls to WM_GETTEXT from another process for Edit controls (TextBox controls in .NET) with the ES_PASSWORD style set return an empty string (or NULL - I don't remember)...and get a life! :mad: If you're not a cracker, ignore the above statement except the bit about password fields in other processes! :)

-----BEGIN GEEK CODE BLOCK----- Version: 3.21 GCS/G/MU d- s: a- C++++ UL@ P++(+++) L+(--) E--- W+++ N++ o+ K? w++++ O- M(+) V? PS-- PE Y++ PGP++ t++@ 5 X+++ R+@ tv+ b(-)>b++ DI++++ D+ G e++>+++ h---* r+++ y+++ -----END GEEK CODE BLOCK-----

[Andreas Philipson]

Thanks for the help! I'll try it when I get home. And regarding my use of this code - I'm trying to create a Password Manager which allows Drag&Drop to any edit control. Andreas Philipson

[Andreas Philipson]

After changing the solution to

[DllImport("user32.dll", CharSet=CharSet.Ansi)]
static extern int SendMessage(IntPtr hWnd, int msg, int wParam, [Out]StringBuilder lParam);

It works perfectly! Thanks again! Andreas Philipson