How to create JSON webservice in ASP.NET

This example will show how to create Webservice using asp.net and the result will return in format JSON(JavaScript Object Notation).

Below is the step by step to create webservice:

1. Open Visual studio.
2. Create New Project
3. Add New File in the solution and choose Web Service file( .asmx)
4. Copy paste code below to create your own JSON webservice

The Web Service Code

/// <summary>
    /// Summary description for KenticoJSONTest
    /// </summary>
    [WebService(Namespace = "http://tempuri.org/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
    [System.ComponentModel.ToolboxItem(false)]
    // To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. 
    [System.Web.Script.Services.ScriptService]
    public class AjaxWebService : System.Web.Services.WebService
    {

        [WebMethod]
        public string HelloWorld()
        {
            return "Hello World";
        }

        [WebMethod]
        [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
        public String getState(string Country)
        {
            string retJSON = "";
            SqlConnection dbConn = new SqlConnection("<Connection String>");
            SqlDataAdapter dbAdapter = null;
            string sql = "SELECT STATE_FULL_NAME,STATE_SHORT_NAME FROM STATE WHERE COUNTRY LIKE '%" + Country + "%'";

            DataTable returnTable = new DataTable("State");
            dbConn.Open();
            dbAdapter = new SqlDataAdapter(sql, dbConn);
            dbAdapter.Fill(returnTable);
            dbConn.Close();

            retJSON = GetJson(returnTable);
            return retJSON;
        }


        private string GetJson(DataTable dt)
        {
            JavaScriptSerializer serializer = new JavaScriptSerializer();
            List<Dictionary<string, object>> rows =
              new List<Dictionary<string, object>>();
            Dictionary<string, object> row = null;

            foreach (DataRow dr in dt.Rows)
            {
                row = new Dictionary<string, object>();
                foreach (DataColumn col in dt.Columns)
                {
                    row.Add(col.ColumnName.Trim(), dr[col]);
                }
                rows.Add(row);
            }
            return serializer.Serialize(rows);
        }

    }

Example Output

"[{"FULL_NAME":"NEGERI SEMBILAN","SHORT_NAME":"N. SEMBILAN"},{"FULL_NAME":"WILAYAH PERSEKUTUAN KUALA LUMPUR","SHORT_NAME":"KUALA LUMPUR"},{"FULL_NAME":"MELAKA","SHORT_NAME":"MELAKA"}]"

By Mohd Zulkamal
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