How to check that string is alphanumeric or not in vb.net and C#

Alphanumeric is a combination of alphabetic and numeric characters.The alphanumeric character set consists of the numbers 0 to 9 and letters A to Z. for example these are the alphanumeric:

1. Author123
2. author5Code
3. 123456TY
4. 897AUTOR
suppose if you want to know that particular string is a alphanumeric or not than you can use following code sample

[VB.Net]

Private Function IsAlphaNum(ByVal strInputText As String) As Boolean
   return System.Text.RegularExpressions.Regex.IsMatch(strInputText, "^[a-zA-Z0-9]+$")
End Function

[C#]

private bool IsAlphaNum(string strInputText)
{
  return System.Text.RegularExpressions.Regex.IsMatch(strInputText, "^[a-zA-Z0-9]+$"); 
}

8 thoughts on “How to check that string is alphanumeric or not in vb.net and C#”

  1. This code is horrible, it doesn’t even come close to meeting the goals of this simple function.  For example “123” is not Alpha Numeric?  How about “AA-&^^^%%-12”?

  2. wow just came across this code – ouch

    if you want an alphanumeric checker you need

    // ans – (a)lpha (n)umeric (s)tring is our flag to see if it is or isnt

    dim ans as boolean = true

    For i = 0 To str.Length – 1

    //if you need to include spaces you needto add ‘ or str(i) = ” ” ‘ to the next line – please note that this is not a secure method for cleansing strings just a quick hack around the example!

    If not Char.IsLetter(str(i)) or Char.IsNumber(str(i)) Then

    ans = false

    End If

    Next

    if ans = true
    //yey its alphanumeric
    else
    //boo it isnt
    end if

  3. Ooops – you should also exit the loop

    so after “ans = false”

    put

    “exit for”

    otherwise you are wasting processor time.

  4. Wow this is the worst function ever, seriously this should be deleted, cant believe this pile of crap came up number 1 on google for my search, useless

  5. Be simpler to just return System.Text.RegularExpressions.Regex.IsMatch(strInputText, “^[a-zA-Z0-9]+$”) rather than declaring the variable, initializing it to a value that is never used, and then having an IF.

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