using System;
using System.Collections.Generic;
using System.Linq;
using System.Data;
using System.Data.SqlClient;


namespace WebServiceTest
{
    public class DBOperator : IDisposable
    {
        public static SqlConnection conn;
        private string ConnStrig = @"Data Source=.;Initial Catalog=SDTI.TicketDB;Integrated Security=True";

        public DBOperator()
        {
            if (conn == null)
            {
                conn = new SqlConnection();
                conn.ConnectionString = ConnStrig;
                conn.Open();
                if (conn.State == ConnectionState.Open)
                {
                    
                }
            }
        }


        public List<string> Select()
        {
            List<string> list = new List<string>();

            try
            {
                string sql = "select * from table";
                SqlCommand cmd = new SqlCommand(sql, conn);
                SqlDataReader read = cmd.ExecuteReader();
                while (read.Read())
                {
                    list.Add(read[0].ToString());
                    list.Add(read[1].ToString());
                    list.Add(read[2].ToString());
                    list.Add(read[3].ToString());

                }
                read.Close();
                cmd.Dispose();
            }
            catch (Exception e)
            {
                string y = e.Message;
            }
            return list;
        }

        public void Dispose()
        {
            if (conn != null)
            {
                conn.Close();
                conn = null;
            }
        }

    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;

namespace WebServiceTest
{
    /// <summary>
    /// WebService1 的摘要说明
    /// </summary>
    [WebService(Namespace = "http://tempuri.org/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
    [System.ComponentModel.ToolboxItem(false)]
    // 若要允许使用 ASP.NET AJAX 从脚本中调用此 Web 服务，请取消注释以下行。 
    // [System.Web.Script.Services.ScriptService]
    public class WebService1 : System.Web.Services.WebService
    {
        DBOperator op = new DBOperator();

        [WebMethod]
        public string HelloWorld()
        {

            return "Hello World";
        }

        [WebMethod(Description = "Test")]
        public List<string> Test()
        {           
            return op.Select();
        }

    }
}

using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data.Entity;
using System.Data;

namespace DBWebService
{
    public class SDTIContext : DbContext
    {
        public SDTIContext() : base("SDTIDB")
        {
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace DBWebService
{
    public class DBOperator
    {
        SDTIContext db = new SDTIContext();

        public List<SDTI_TicketType> GetDB()
        {
            return db.Set<SDTI_TicketType>().GroupBy(x => x.TypeNO).Select(x => x.FirstOrDefault()).ToList();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;

namespace DBWebService
{
    /// <summary>
    /// WebService 的摘要说明
    /// </summary>
    [WebService(Namespace = "http://tempuri.org/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
    [System.ComponentModel.ToolboxItem(false)]
    // 若要允许使用 ASP.NET AJAX 从脚本中调用此 Web 服务，请取消注释以下行。 
    // [System.Web.Script.Services.ScriptService]
    public class WebService : System.Web.Services.WebService
    {
        DBOperator db = new DBOperator();
        [WebMethod]
        public List<SDTI_TicketType> HelloWorld()
        {
            return db.GetDB();
        }
    }
}