How to disable Special Characters and Number in textbox?

Question

For example in my form I will need to input my name in a textbox but when there's a special character or number in a textbox or a number, a messagebox will pop up saying that "Please type a valid name" after pressing the button.

Wow I didn't think about that but I will make a local application where the peoples name are Alphabetical. — leimelson06
– leimelson06, Commented Mar 5, 2016 at 2:30

Ian · Accepted Answer · 2016-03-05 05:31:31Z

4

To avoid it doing wrong recognition when someone enters a non-ASCII character but valid name (such as 田中太郎), you may need to really list down the special characters you don't want to include.

But to keep it simple, if what you mean by special characters are all other than white space and alphabet, then simply use built-in function char.IsLetter and char.IsWhiteSpace:

if (str.Any(c => !char.IsLetter(c) && !char.IsWhiteSpace(c))){
    //invalid
} else {
    //valid
}

If you want to check for some specific range of characters and not others given the above checking, simply put your additional checking in the //invalid part:

if (str.Any(c => !char.IsLetter(c) && !char.IsWhiteSpace(c))){
    //possible invalid
    if (some additional character range checking){
        //valid case
    } else {
        //truly invalid
        //add as many else if as you want
    }
} else {
    //valid
}

edited Mar 5, 2016 at 5:31

answered Mar 5, 2016 at 2:19

Ian

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5 Comments

leimelson06 Over a year ago

How do i use this? for example my txtbox name is FN?

leimelson06 Over a year ago

and it says ) expected

Ian Over a year ago

@leimelson06 it should be triple closing parenthesis ))) instead of two )) now it should be OK. Get the str from your TextBox.Text, for example: string str = textBoxFullName.Text; or string str = FN.Text then you can apply the above checking.

leimelson06 Over a year ago

Thank you. You really helped me.

Ian Over a year ago

@leimelson06 no problem! glad that I can be of any help. :)

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