ajax参数始终为null？

Question

I am trying to pass the a string to my behind code, but its always null.

$.ajax({
   type: "POST",
   url: "Search.aspx?do=SearchText",
   data: {searchText: searchText },
   contentType: "application/json; charset=utf-8",
   dataType: "json",
   success: fnsuccesscallback,
   error: fnerrorcallback
});



protected void Page_Load(object sender, EventArgs e)
 {
    if (Request["do"] != null && Request["do"] == "SearchText")
    {
       string result = Search.searchText(Request["searchText"]);
    }
 }

My Request["searchText"] is always null.

EDIT:

---

public void DoSearch(string SearchText)
{
    string result = Search.searchText(SearchText);
}

and in the ajax post:

 url: "Search.aspx/DoSearch",
 data: { searchText: searchText },

Answer 1

The problem with this is you are trying to grab the querystring within the Page_Load event which fires before the ajax code. So on Page_Load there is no parameter passed at that stage which is why it will always be null.