alphanumeric validator

[SIMIN]

Hello,

I've been asked to validate the content of a text box to make sure it's only alphanumeric.

Now I have 2 question on this from you experts:

 

1. alphanumeric value needs to start with alpha or it can start with numbers also?

 

2. I wrote the following code to test my entry but it's somewhere wrong I cannot understand! How can I go through each character to make sure it's alphanumeric?

 

For MyLoop As Integer = 0 To PasswordTextBoxX.Text.Length - 1
   If PasswordTextBoxX.Text.Substring(MyLoop, 1) <= "a" Or PasswordTextBoxX.Text.Substring(MyLoop, 1) >= "z" And _
      PasswordTextBoxX.Text.Substring(MyLoop, 1) <= "A" Or PasswordTextBoxX.Text.Substring(MyLoop, 1) >= "Z" And _
      PasswordTextBoxX.Text.Substring(MyLoop, 1) <= "0" Or PasswordTextBoxX.Text.Substring(MyLoop, 1) >= "9" Then
       MsgBox("invalid")
   End If
Next

[PlausiblyDamp]

You could check each character using the Char.IsLetterOr Digit function, or a regular expression match could be used

 

       If Regex.Match(PasswordTextBoxX.Text, "^[a-zA-Z0-9]+$").Captures.Count > 0 Then
           'is alphanumeric 
       End If

[snarfblam]

If you want to see if a particular character is alphanumeric you can use the Char.IsLetterOrDigit().