Text input limitation C#

Of course that's possible, e.g.:


Use Char.IsLetterOrDigit(char), you need to use the KeyPress event to get the characters and cancel (Handled) the event.

Do you need further help?

Thanks for the prompt reply.
Can I use this Char.IsLetterOrDigit(char) methold to check for the 1st letter in the texbox when my button click event activates?
And if I use Char.IsLetterOrDigit(char) do I have to input every ".,./'!@#$$..." under "char" I want to filter?

Well if u want to check on click of button, you might also consider using regular expressions, if it is possible.

Hi informaniac can you elaborate what you mean by using regular expressions?

Not sure if I understand your question: "And if I use Char.IsLetterOrDigit(char) do I have to input every ".,./'!@#$$..." under "char" I want to filter? ".

Did you try my code? If not - try. You won't be able to enter any chars except digits and letter. That's simple.

informaniac has a point. What happens if you enter text by using ctrl-V? The approach I showed will not work. In other words you need to check entire block of inserted text and chack for invalid characters.
In this case you need to use what's called regular expressions, e.g.

http://www.radsoftware.com.au/articles/regexlearnsyntax.aspx

Not very easy unfortunately if you are not familiar to the concept.

OK, about Char.IsLetterOrDigit(char):

char comes from the event argument, it corresponds to a key pressed.

Yes, anarki_jimbel it works but is there a way to enable the "Backspace" key?

It's possible:

'\b' - denotes backspace.
Or you may use a number 8

        private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (!char.IsLetterOrDigit(e.KeyChar) && e.KeyChar!= '\b')//
            {
                e.Handled = true;
            }
        }

Select allOpen in new window