Question

How can I use a MaskedTextBox to prevent the user from entering an invalid IP address? (I want it to behave just like the Windows one).

Answer 1

Try this:

IPAddress ipAddress;
if (IPAddress.TryParse(maskedTextBoxY.Text, out ipAddress))
{
    //valid ip
 }
else
 {
    //is not valid ip
}

note: to use it, you need import the System.Net namespace:

using System.Net;