Question

How do I add ASP.NET validation in C# all three text boxes aren’t empty and the phone number has the format of DDDD-DDDD where D is 0 – 9?

<asp:TextBox ID="txtFirstName" runat="server"></asp:TextBox>
<asp:TextBox ID="txtLastName" runat="server"></asp:TextBox>
<asp:TextBox ID="txtPhoneNumber" runat="server"></asp:TextBox>

Answer 1

Have you tried to solve this problem yourself? The documentation is easy to find:

http://msdn.microsoft.com/en-us/library/aa479013.aspx

You need to use a required field validator — something like this:

 <asp:RequiredFieldValidator 
         id="RequiredFieldValidator1" runat="server" 
         ErrorMessage="Required!" 
         ControlToValidate="txtFirstName">

You will also want a regular expression validator, something like:

<asp:RegularExpressionValidator id="RegularExpressionValidator1" 
   runat="server" ControlToValidate="txtPhoneNumber" 
    ErrorMessage="wrong!" 
    ValidationExpression="^\d\d\d\d-\d\d\d\d$">
</asp:RegularExpressionValidator>

NB The toolbox for reg expression has many built in, including most phone number formats. I would just use one of those.