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MS Access: Test a string for an alphanumeric value

Question: In Microsoft Access, I want to know if a string value contains alphanumeric characters only. How can I do this?

Answer: To accomplish this, you need to create a custom function.

You'll need to open your Access database and create a new module.

Then paste into the new module the following function:

Function AlphaNumeric(pValue) As Boolean

   Dim LPos As Integer
   Dim LChar As String
   Dim LValid_Values As String

   'Start at first character in pValue
   LPos = 1

   'Set up values that are considered to be alphanumeric
   LValid_Values = " abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ+-.0123456789"

   'Test each character in pValue
   While LPos <= Len(pValue)

      'Single character in pValue
      LChar = Mid(pValue, LPos, 1)

      'If character is not alphanumeric, return FALSE
      If InStr(LValid_Values, LChar) = 0 Then
         AlphaNumeric = False
         Exit Function
      End If

      'Increment counter
       LPos = LPos + 1

   Wend

   'Value is alphanumeric, return TRUE
   AlphaNumeric = True

End Function

The AlphaNumeric function will return TRUE if all of the values in the string are alphanumeric. Otherwise, it will return FALSE.

You can use the AlphaNumeric function as follows:

AlphaNumeric("6.49")
Result: TRUE

AlphaNumeric("^Tech on the Net ")
Result: FALSE

AlphaNumeric("hi~there")
Result: FALSE