How can I validate a asp:textbox which starts with alphabet "T" followed by numbers.Please help

T\d*

gives the Capital T followed by zero or more numbers

T\d+

Same as above but will fail unless there is one number. + is 1 or more while * is zero or more.

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William Wegerson (www.OmegaCoder.Com)

Thank you for your reply , but when I try to run that regular expression , it gives me unrecognised escape sequence builderror.
Can you help me on this.I am trying to enter "T12345" kind of value inside the textbox andd trying to validate the same.
My code is :

<asp:TextBox id="txt1" runat="server"/>
<asp:label id="" runat="server"/> and I am using

using

System.Text.RegularExpressions;

on button click

if

(!Regex.IsMatch(txt1.Text,"T\d+"))

{

lblmsg.Text="Error";

}

Build Error:unrecognised escape sequence error.

@"T\d+"

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William Wegerson (www.OmegaCoder.Com)

Thanks, that helped alot but doesnot completely solve my purpose.Is there anything that allows only numbers(0-9) after "T" and no characters or alphabets after that.Because the above also allows alphabets after numbers again.

example:T1234asdf [this is validating this as valid input]

I want like this :T1234 (only numbers and not alphabets after numbers).