You can achieve that through and Ajax request. Since you're using asp.net here is a good starting point for some great JavaScript Ajax libraries for it.
Here's also a simple example of how to make a simple Ajax request.
function sampleAjaxReq(){
var xmlhttp=new XMLHttpRequest();
xmlhttp.open("POST","resource.asp",true);
xmlhttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");
xmlhttp.send("pname1=value1Henry&pname2=value2");
}