How to edit a record using Jquery Ajax??

Question

I want to edit a record but the record was not updated.

 

sp:

 

updatestud

 

ALTER PROCEDURE [dbo].[updatestud]

@studid int,

@studname varchar(50),

@studaddress varchar(50)

AS

BEGIN

update tblstud set studname=@studname,studaddress=@studaddress where studid=@studid;

END

 

 

 Webform1.aspx.cs

 

        public static void EditData(int studid, string studname, string studaddress)
        {
            cn.Open();


            SqlCommand cmd = new SqlCommand("updatestud", cn);
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.AddWithValue("@studid", studid);
            cmd.Parameters.AddWithValue("@studname", studname);
            cmd.Parameters.AddWithValue("@studaddress", studaddress);

            int i = cmd.ExecuteNonQuery();

            if (i > 0)
            {
                Console.WriteLine("Update Successfully");
            }
            else
            {
                Console.WriteLine("Not Update Successfully");
            }

            cn.Close();

        }

Webform1.aspx

 

                    //for getdatalist
                    function GetData() {
                        $.ajax({

                            url: 'WebForm1.aspx/GetData',
                            type: 'post',
                            contentType: 'application/json;charset=utf-8',
                            datatype: 'json',
                            data: "{}",
                            success: function (data) {
                                data = JSON.parse(data.d);
                                for (var i = 0; i < data.length; i++) {
                                    $("#tbl").append('' + data[i].studname + '  ' + data[i].studaddress + '  + data[i].studid + ', \'' + data[i].studname + '\' ,\'' + data[i].studaddress + '\')" /> ')
                                }
                            },
                            error: function () {
                                alert('Not Get Data')
                            },
                        });
                    }

                    //when I click on edit button then record going to form and then some changes in record and then press update then give an error   Uncaught ReferenceError: studid is not defined?
                    function Update(studid, studname, studaddress) {

                        $.ajax({

                            url: 'WebForm1.aspx/EditData',
                            type: 'post',
                            contentType: 'application/json;charset=utf-8',
                            datatype: 'json',
                            data: "{studid: '" + studid + "',studname:'" + $("#txtname").val() + "',studaddress:'" + $("#txtaddress").val() + "'}",
                            success: function (data) {

                                data = JSON.parse(data.d);

                                studid = studid;

                                $("#txtname").val(studname);
                                $("#txtaddress").val(studaddress);

                                if (studid != null) {

                                    $("#btnupdate").val("Update");

                                }

                                studid = studid;
                            },
                            error: function () {
                                alert('Update Error');
                            },

                        });
                    }

//when I click on edit button then record going to form and then some changes in record and then press update then give an error Uncaught ReferenceError: studid is not defined?

 

when i press on update then record going to form but again click on update then give an error

 

Response {"d":null}

 

WebForm1.aspx:84 Uncaught ReferenceError: studid is not defined

 

how to solve this issue??