Cascaded dropdown using jQuery

using System;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Web.Services;
using System.Data.OracleClient;
using System.Text;
using System.Collections.Generic;
public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    [WebMethod]
    //public static List<string> GetDate(string x, string y)
    public static Dictionary<string, object> GetFileType(string x, string y)
    {
        try
        {
            Dictionary<string, object> dd = new Dictionary<string, object>();
            dd = GetFromDataBase("Select FiletypeId,Filetypename from M_FileType");
            return dd;
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
  
    [WebMethod]
    public static Dictionary<string, object> GetFileColumn(string Param)
    {
        try
        {
            Dictionary<string, object> dd = new Dictionary<string, object>();
            dd = GetFromDataBase("Select FilecolId,Name from M_FileColumn where filetypeid='" + Param + "'");
            return dd;

        }
        catch (Exception ex)
        {
            throw ex;
        }

    }

    [WebMethod]
    public static Dictionary<string, object> GetValidations(string Param)
    {
        try
        {
            Dictionary<string, object> dd = new Dictionary<string, object>();
            dd = GetFromDataBase("SELECT m_v.validationname as ValidationName, m_v.validationid as ValidationID FROM m_filecolvalidation_map m_f, m_validation m_v WHERE (m_v.validationid = m_f.validationid) AND FILECOLID='" + Param + "'");
            return dd;

        }
        catch (Exception ex)
        {
            throw ex;
        }

    }

    private static Dictionary<string, object> GetFromDataBase(string Query)
    {
        try
        {
            DataSet ds = new DataSet();
            OracleConnection oCon = new OracleConnection("Password=LIFECONNECT_DEV;Persist Security Info=True;User ID=LIFECONNECT_DEV;Data Source=KOTAK.BZNMUM.COM");
            OracleCommand oCmd = new OracleCommand(Query, oCon);
            OracleDataAdapter da = new OracleDataAdapter(oCmd);
            da.Fill(ds);
          //  string ss= HimJSON.GetJSONString(ds.Tables[0]);
     
          return  HimJSON1.ToJson(ds.Tables[0]);
          
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
}