Validating a string in a textbox.

Question

Hi, I am trying to validate a string that has been inputted into a text box to make sure there is nothing but alphabetical charecters in the textbox. The following code only checks the first character in the textbox...

If Char.IsLetter(textbox1.Text) = False Then
            MsgBox("Error! Invalid charecters present")
            Exit Sub
        End If

I was wondering if there was any way that i could turn this into some sort of loop so that it checks all of the charecters present within the textbox?

Answer 1

Hello,

you can use the like Operator

regards Ellen

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Ich benutze/ I'm using VB2008 & VB2010

Answer 2

You can either validate the input as the user types in each character or you can validate it after the user has done typing.

For the first one, you handle one of the textbox's keyboard events (keypress, keydown or keyup) and test the typed-in character. If it's not what you want, you can show a message and set e.Handled = True so that the bad character is ignored.

For the 2nd method, you loop thru all the character in the input string and test each one to see if its in a not allowed group of characters. If it is, you exit the loop and show the message to your user. Something like this:

Dim input as string = textbox1.text

Dim notAllowedChars as String = "~`!@#$%^&*()_-+={[]}|\;':""<,>.?/1234567890"

For each c as Char in input

   If notAllowedChars.Contains(c) Then

        MessageBox.Show("Invalid charaters present")

        Exit For

    End If

Next

Answer 3

The first method works perfectly!! Thanks for the help!