Error Method 500 ajax cascading dropdownlist

See more:

C#

Here is my code ..
when I run it comes error method 500..


using System;
using System.Collections;
using System.Web;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.Data.SqlClient;
using System.Collections.Generic;
using System.Collections.Specialized;
using AjaxControlToolkit;
using System.Configuration;
using System.Data;

///

/// Summary description for DropdownWebService
///

[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.Web.Script.Services.ScriptService()]
public class DropdownWebService : System.Web.Services.WebService
{

[WebMethod]
public CascadingDropDownNameValue[] BindCountrydropdown(string knownCategoryValues, string category)
{
SqlConnection concountry = new SqlConnection(ConfigurationManager.ConnectionStrings["Connection"].ConnectionString);
concountry.Open();
SqlCommand cmdcountry = new SqlCommand("select * from Country", concountry);
SqlDataAdapter dacountry = new SqlDataAdapter(cmdcountry);
cmdcountry.ExecuteNonQuery();
DataSet dscountry = new DataSet();
dacountry.Fill(dscountry);
concountry.Close();
List<cascadingdropdownnamevalue> countrydetails = new List<cascadingdropdownnamevalue>();
foreach(DataRow dtrow in dscountry.Tables[0].Rows)
{
string CountryID = dtrow["CountryId"].ToString();
string CountryName = dtrow["Country"].ToString();
countrydetails.Add(new CascadingDropDownNameValue(CountryName,CountryID));
}
return countrydetails.ToArray();
}
[WebMethod]
public CascadingDropDownNameValue[] BindStatedropdown(string knownCategoryValues, string category)
{
int CountryID;
StringDictionary countrydetails = AjaxControlToolkit.CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);
CountryID = Convert.ToInt32(countrydetails["Country"]);
SqlConnection constate = new SqlConnection(ConfigurationManager.ConnectionStrings["Connection"].ConnectionString);
constate.Open();
SqlCommand cmdstate = new SqlCommand("select * from countryState where CountryId=@CountryId", constate);
cmdstate.Parameters.AddWithValue("@CountryId", CountryID);
cmdstate.ExecuteNonQuery();
SqlDataAdapter dastate = new SqlDataAdapter(cmdstate);
DataSet dsstate = new DataSet();
dastate.Fill(dsstate);
constate.Close();
List<cascadingdropdownnamevalue> statedetails = new List<cascadingdropdownnamevalue>();
foreach (DataRow dtstaterow in dsstate.Tables[0].Rows)
{
string stateID = dtstaterow["StateId"].ToString();
string statename = dtstaterow["State"].ToString();
statedetails.Add(new CascadingDropDownNameValue(statename, stateID));
}
return statedetails.ToArray();
}
[WebMethod]
public CascadingDropDownNameValue[] BindRegiondropdown(string knownCategoryValues, string category)
{
int stateID;
StringDictionary statedetails = AjaxControlToolkit.CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);
stateID = Convert.ToInt32(statedetails["State"]);
SqlConnection conregion = new SqlConnection(ConfigurationManager.ConnectionStrings["Connection"].ConnectionString);
conregion.Open();
SqlCommand cmdregion = new SqlCommand("Select * from stateCity where StateId=@StateId", conregion);
cmdregion.Parameters.AddWithValue("@StateId", stateID);
cmdregion.ExecuteNonQuery();
SqlDataAdapter daregion = new SqlDataAdapter(cmdregion);
DataSet dsregion = new DataSet();
daregion.Fill(dsregion);
conregion.Close();
List<cascadingdropdownnamevalue> regiondetails = new List<cascadingdropdownnamevalue>();
foreach (DataRow dtregionrow in dsregion.Tables[0].Rows)
{
string regionID = dtregionrow["CityId"].ToString();
string regionname = dtregionrow["City"].ToString();
regiondetails.Add(new CascadingDropDownNameValue(regionname,regionID));

}
return regiondetails.ToArray();
}
}