C＃中的应用程序级键过滤器

Question

I want my Win-Forms application (which has many different forms) to accept only certain characters of user input. This restriction should apply to all forms, all input fields, etc. Is there any simple solution to implement this without adding keyboard-events to every single form and even better, without changing any existing form?

First I have thought of a low-level keyboard hook but this would be applied globally to every user input in every application running on the system which isn't the ideal solution, I guess. Any other possibilities or suggestions?

Answer 1

You can do that if you create a custom control for each control you need and set your control to inherit the core controls. For example, this code will prevent clicking on zero:

public class MyTextBox : TextBox
{
    protected override void OnKeyUp(KeyEventArgs e)
    {
        if (e.KeyCode == Keys.D0)
            e.SuppressKeyPress = true;
    }
}

You can even drag this control from the toolbox (after you build).