How to make a textbox non-selectable using C#

Question

I\'m using C#/.NET for a Windows Forms application. I have a text box. How can I make the text box unselectable?

I don\'t want to disable the complete textbox.

Answer 1

The messages that cause text can be intercepted and blocked. I would have thought that EM_SETSEL would be all that is required. However, even when the mouse clicks and drags, there is no EM_SETEL message, but the text still selects. Possibly one of the messages has a pointer to a struct that contains the info.

Note: I'm not sure if this prevents all ways to select text.

public class TextBox2 : TextBox {

    private const int EM_SETSEL = 0x00B1;
    private const int WM_LBUTTONDBLCLK = 0x203;
    private const int WM_MOUSEMOVE = 0x200;
    private const int WM_KEYDOWN = 0x100;
    private const int VK_CONTROL = 0x11;
    private const int VK_SHIFT = 0x10;

    public TextBox2() {
        this.ShortcutsEnabled = false; // disabled right click menu
        this.Cursor = Cursors.Default;

    }

    protected override void OnGotFocus(EventArgs e) {
        base.OnGotFocus(e);
        HideCaret(this.Handle); // doesn't work from OnHandleCreated
    }

    [DllImport("user32.dll")]
    public static extern bool HideCaret(IntPtr hWnd);

    public override bool PreProcessMessage(ref Message msg) {
        // prevents the user from using the SHIFT or CTRL + arrow keys to select text
        if (msg.Msg == WM_KEYDOWN)
            return true;

        return base.PreProcessMessage(ref msg);
    }

    protected override void WndProc(ref Message m) {
        if (m.Msg == EM_SETSEL || m.Msg == WM_MOUSEMOVE || m.Msg == WM_LBUTTONDBLCLK)
            return;

        base.WndProc(ref m);
    }
}