VB.NET校验字符串函数

'Validate for a date
Shared Function checkdate(ByVal thisvalue As String) As String
  If Not IsDate(thisvalue) Then
    checkdate = "NULL"
  Else
    checkdate = "'" & thisvalue & "'"
  End If
  Return checkdate
End Function ' END checkdate

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
'Used to submit values to the database, check for empty value, replace w/ "NULL"
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
Shared Function checkNumber(ByVal thisvalue As String) As String
  If IsDBNull(thisvalue) Or Len(thisvalue) = 0 Or Not IsNumeric(thisvalue) Then
    checkNumber = "NULL"
  Else
    checkNumber = thisvalue
  End If
  Return checkNumber
End Function ' END checkNumber