CascadingDropDown控件读数据库不出东西
using   System;
using   System.Web;
using   System.Collections;
using   System.Configuration;
using   System.Collections.Generic;
using   System.Collections.Specialized;
using   System.Web.Services;
using   System.Web.Services.Protocols;
using   AjaxControlToolkit;
using   System.Data;
using   System.Data.SqlClient;
/**/
///   <summary>

///   Summary   description   for   Northwind

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

        [WebMethod]
        public   CascadingDropDownNameValue[]   GetEmployees(string   knownCategoryValues,   string   category)
        {
                string   connectionString   =   ConfigurationManager.ConnectionStrings[ "Northwind "].ConnectionString;
                SqlConnection   connection   =   new   SqlConnection(connectionString);
                SqlCommand   command   =   new   SqlCommand( "SELECT   *   FROM   Employees ");
                command.Connection   =   connection;
                connection.Open();
                SqlDataAdapter   adapter   =   new   SqlDataAdapter(command);
                DataSet   dataSet   =   new   DataSet();
                adapter.Fill(dataSet);
                command.Connection.Close();
                DataTable   tbl   =   dataSet.Tables[0];
                List <CascadingDropDownNameValue>   values   =   new   List <CascadingDropDownNameValue> ();
                foreach   (DataRow   dr   in   tbl.Rows)
                {
                        string   sEmployee   =   (string)dr[ "FirstName "]   +   "   "   +dr[ "LastName "];
                        int   iEmployee   =   (int)dr[ "EmployeeID "];
                        values.Add(new   CascadingDropDownNameValue(sEmployee,   iEmployee.ToString()));
                }
                return   values.ToArray();

        }