Hi...
validate textbox with RegularExpressionValidator like blow.
its allow only numeric values only into textbox.
<asp:RegularExpressionValidator ID="rxv1" runat="server"
ErrorMessage="Pls enter Numerics Only" EnableClientScript="true"
ControlToValidate="txtbox" ValidationExpression="\d+"></asp:RegularExpressionValidator>
see may its helpful to u.
thank u.