Webservice without using Entity, only using Datatable with JsonConvert and returning JSON (with data table)

 reference :- https://www.c-sharpcorner.com/article/how-to-convert-and-bind-json-string-in-to-asp-net-gridview-with-c-sharp/

[WebMethod]

    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]

        public string HelloWorld()

    {

        String conStr = ConfigurationManager.ConnectionStrings["connectionString"].ConnectionString;

        using (SqlConnection con = new SqlConnection(conStr))

        {

            using (SqlCommand cmd = new SqlCommand("Select * from aggregate._form_info", con))

            {

             

                con.Open();

                SqlDataReader dr = cmd.ExecuteReader();

                

                DataTable dt = new DataTable();

                dt.Load(dr);

             string json = JsonConvert.SerializeObject(dt);

            return json;

        //convert from JSON to object

                //DataTable myObjectDT = JsonConvert.DeserializeObject<DataTable>(json);

               // JavaScriptSerializer js1 = new JavaScriptSerializer();

                 //return JsonConvert.SerializeObject(myObjectDT);

            //without returning function, below code

                    //Context.Response.Write(json);

                con.Close();

            }

        }

    }

-------------------**************------------------------

web.config connection string

<configuration>

<connectionStrings>

<add name="connectionString" connectionString="initial catalog=aggregate;user=sa1;password=sa;data source=." />

</connectionStrings>

</configuration>

--------------------*************************--------------------------------

Output in JSON