how to get database values in dropdownlist in jqgrid in javascript using ajax json,and also how to write the code formediting in jqgrid....iam not understand trirand wiki website.....can u explain...

$(document).ready(function () {

 var comapnysearch;
    $.ajax({ type: "POST",
        url: 'EmployeeDetails.aspx/comapanynamesearch',
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        async: false,
        success: function (msg) {
            companynames = msg.d;
        }
    });

[WebMethod(EnableSession = true)]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
public static string comapanynamesearch()
    {
        try
        {
            string strJson = string.Empty;
            abs_properties_getprofiledetails obp = new abs_properties_getprofiledetails();
            abs_sqldb_comapanysearch obl = new abs_sqldb_comapanysearch();
            stringjson json = new stringjson(); //stringjson is  class file.it convert datatable to string format..//
            DataTable dt = obl.getEmployeeDetails(obp);
            if (dt.Rows.Count > 0)
            {
                strJson = json.json_string(dt);
            }
            return strJson;
        }

        catch (Exception ex)
        {
            throw (ex);

        }

public override DataTable comapanynamesearch(abs_properties_getprofiledetails obj)
 {
     try
     {
         SqlConnection vcon = new SqlConnection();
         vcon.ConnectionString = ConfigurationManager.ConnectionStrings["ApplicationServices"].ConnectionString;
         SqlCommand vcmd = new SqlCommand();
         vcmd.Connection = vcon;
         vcmd.CommandType = CommandType.StoredProcedure;
         vcmd.CommandText = "getcomapanynames_sp";
         SqlDataAdapter sda = new SqlDataAdapter();
         DataTable dt = new DataTable();
         sda.Fill(dt);
      
         return dt;
     }
     catch (Exception ex)
     {
         throw (ex);

     }
 }