Javascript calling webservice and ASP.Net Sequence

Question

I`m using Javascript function that uses a web service and after finishing it i have to update a Grid Datasource

To accomplish this task i called the javascript function via RegisterClientScriptBlock then call the UpdateGridDataSource method

But While Debugging i found that it calls the UpdateGridDataSource method first .. Then Call the method in the WebService!

ASP.Net Code

System.Web.UI.ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "delete", "DrawPOI();", true);

UpdateDataSource(); 

JavaScriptCode

function DeletePOI(arg) {
      //Some Code  
        $.ajax({
            url: "JSBLL.asmx/DeletePOI",
            type: "POST",
            dataType: "json",
            contentType: "application/json; charset=utf-8",
            data: "{id:'" + arg + "'}",
            success: function (msg) {
                alert(msg.d);
            },
            error: function (e) {
                alert('Error');
            }
        }); //some code
        return false;
    }

WebService :

[WebMethod]
        [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
        public string DeletePOI(string ID)
        try
            {
                if (id == "")
                    throw new Exception();

                long ID = Convert.ToInt64(id);
                using (GuardEntities database = new GuardEntities())
                {
                    var poi = database.POIs.Where(x => x.ID == ID).FirstOrDefault();

                    database.POIs.DeleteObject(poi);
                    database.SaveChanges();
                }

                return "POI Deleted Successfully";
            }
            catch
            {
                return "Error Occured";
            }
}

The Problem is that UpdateDataSource() is called before DeletePOI(string ID)

Answer 1

Javascript code registered with RegisterClientScriptBlock() runs on the client in the browser. ASP.NET code runs on the server.

When it gets to the line:

System.Web.UI.ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "delete", "DrawPOI();", true);

It says, when the page loads on the client, call DrawPOI(). It then immediately runs the next line of code:

UpdateDataSource(); 

When it's done with all the ASP.NET code, it then sends your page to the client. Basically, what you are trying to do will not work. You can't call client-side Javascript in the middle of your server-side ASP.NET code and wait for it to return.

What you can do is call the web service directly from your server-side code.