Web Method Syntax For Jquery Ajax In Asp

$.ajax({
type: "POST",
url: "jquerychat.aspx/SendMessage",
data: "{msg:'Hello',userId:1}",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function (msg) {
// Replace the div's content with the page method's return.
// $("#txtMessages").val(msg.d);msg:'Hello',
},
error: function(){
alert('failure');
}
});
});
[WebMethod]
public static string SendMessage(string msg,int userId )
{
NameValueCollection nvc = HttpContext.Current.Request.Form;...................