Either you can write your print related code in code behind and then inject it into the page:
How to Print in ASP.NET 2.0[
^]
OR using JavaScript directly on the page itself, like:
function CallPrint()
{
var printContent = document.getElementById('<%= pnlToPrint.ClientID %>');
var printWindow = window.open("", "Print Panel", ‘left=50000,top=50000,width=0,height=0′);
printWindow.document.write(prtContent.innerHTML);
printWindow.document.close();
printWindow.focus();
printWindow.print();
printWindow.close();
}
<asp: Panel runat="server" id="pnlToPrint" >
<table>
<tr>
<td>
Your data
</td>
</tr>
</table>
</asp: Panel>
<input type="button" value="Print" onclick="CallPrint();" />
Above code prints just the content inside the panel - can be a grid or even just a label.