Use Regular expression to validate a Phone number : Regular Expression « Validation « ASP.NET Tutorial

   <form runat="server">
      <asp:Label id="lblMessage" runat="server" /><br>
      <asp:Panel id="Panel1" runat="server">
            <td valign="top">Phone (<i>xxx-xxxx</i>):</td>
            <td valign="top">
               <asp:TextBox id="tbPhone" runat="server"
                  size=11 /><br>
               <asp:RegularExpressionValidator runat="server"
                  ErrorMessage="That is not a valid phone" />

            <td colspan="2" valign="top" align="right">
               <asp:Button id="Submit" runat="server" 
                  text="Add" />

8.9.Regular Expression
8.9.1.The predefined character classes
8.9.2.quantifiers used to create patterns that match a variable number of characters at a certain position in the string
8.9.3.Metacharacters for Matching Single Characters
8.9.4.Metacharacters for Matching Types of Characters
8.9.6.Commonly Used Regular Expressions
8.9.7.RegularExpressionValidator compares value against a regular expression
8.9.8.Regular Expression based validation (C#)
8.9.9.Use asp:RegularExpressionValidator to check the zip code
8.9.10.Use asp:RegularExpressionValidator to check the email address
8.9.11.Use Regular expression to validate a Phone number