textbox inside some letters are present like xyz@example.com

For non-web based solutions, see here: https://msdn.microsoft.com/en-us/library/vstudio/bb613590(v=vs.100).aspx[^] and here: WaterMark TextBox For Desktop Applications Using C#, .NET 3.5 and VS2008[^]

For myself,There are two ways to show the user,what to be fill on the textbox..

1.in asp toolkit on you want the letter on the textbox asp tag add placeholder="abc@example.com" like runat="server"
Syntax:

<asp:TextBox ID="txtmailid" runat="server" placeholder="abc@example.com"></asp:TextBox>

Or
2. In ajax toolkit select the textboxwatermarkextender and given the targetcontrol id="id of ur textbox" and watermarktext="abc@example.com"

<asp:TextBox ID="txtmailid" runat="server"></asp:TextBox>
 <ajaxToolkit:TextBoxWatermarkExtender ID="twFname"  runat="server" TargetControlID="txtmailid" WatermarkText="abc@example.com" />

http://www.c-sharpcorner.com/uploadfile/rahul4_saxena/ajax-text-box-watermark-extender/[^]


While in ajax toolkit dont forget to paste toolscript manager or script manager..

placeholder="Enter Name


it may help you.