If you look at the documentation of the RangeValidator
, it appears you can specify a string type:
<asp:RangeValidator runat="server"
MaximumValue="zz"
MinimumValue="xx"
Type="String"
... />
Although you may be better off using a RegularExpressionValidator
. In this example, you'd have:
<asp:RegularExpressionValidator runat="server"
ValidationExpression="^[x-z]{2}$"
... />