how do I format a phone number in textbox while typeing?

Hi,
Use Masked Input Plugin...Here is the code and demo link.
http://digitalbush.com/projects/masked-input-plugin/
Hope This will help You.

First

Imports System.ComponentModel

 
Then

Dim MaskPhone As New MaskedTextProvider("0000-0000") 'Here you use the number of caracters

 
So when the value it will come up with mask
When typing you can use that to my JS would be the simplest solution.
 
In Source you add the event "onKeyUp"
Exemple:

<asp:TextBox ID="TextBoxPHONE" runat="server" CssClass="textbox" Width="65px" onKeyUp="Mascara('PHONE',this,event);" MaxLength="10" TabIndex="31" ></asp:TextBox></td>

 
And the following function:
 

if (key! key = 9 &&! ​​= 8) {
         switch (type) {
case 'PHONE':
                 if (tam> = 5 && tam <9)
                     campo.value s.substr = (0, 4) + '-' + s.substr (4, 4);
                 if (tam> = 6 && tam == 10)
                     campo.value s.substr = (0, 5) + '-' + s.substr (5, 4);
                 break;
             }
     }

you can use masked textbox
 
http://msdn.microsoft.com/en-us/library/kkx4h3az.aspx[^]
 
http://www.dotnetperls.com/maskedtextbox[^]