如何使KeyPress事件处理程序可用于所有表单？

Question

I've created a KeyPress event handler that prevents the entry of anything but digits, decimals, and backspace in any subscibing input control. The problem is that the handler is only available to the form within which it was created. Rather than copying the event handler to every form, is there a way to make it global - so that the keypress event of any input control on any form can subscribe to it.

Thank you.

Answer 1

Another more object oriented solution would be to inherit from the TextBox control and override the KeyPress event, creating your own custom type of TextBox.

class NumericTextBox : System.Windows.Forms.TextBox
{
    protected override void OnKeyPress(System.Windows.Forms.KeyPressEventArgs e)
    {
        base.OnKeyPress(e);

        if (true /* insert your conditions */)
            e.Handled = true;
    }
}

Then use this control where needed in place of the regular TextBox control.

Answer 2

Make it public and static, and you should probably move it to a "Utilities" type class. (Or its own class)

Answer 3

namespace GlobalKeyPress
{
    public class GlobalKeyPress
    {
        public static void KeyPressFilter(object sender, System.Windows.Forms.KeyPressEventArgs e)
        {
            if((e.KeyChar < '0' || e.KeyChar > '9') && e.KeyChar != '.')
                e.Handled = true;
        }
    }
}

Answer 4

Delegates are normal objects, and as such, you can return them from methods.

Specifically, you'd want to create a KeyPressEventHandler delegate

public static class Utilities
{
    private static KeyPressEventHandler handler = KeyPressed;

    public static void KeyPressed(Object sender, KeyPressEventArgs e)
    {
        // Your logic here
    }

    public static KeyPressEventHandler getKeyPressHandler() {
        return handler;
    }
}

Note: I haven't tested this, though. It looks correct as per the pages on Using Delegates and KeyPressEventHandler