读取数据库的数据并转换成List<>

一、在有帮助类DbHelperSQL的时候

1、下为其中返回SqlDataReader的方法

 /// <summary>
         /// 执行查询语句，返回SqlDataReader ( 注意：调用该方法后，一定要对SqlDataReader进行Close )
         /// </summary>
         /// <param name="strSQL">查询语句</param>
         /// <returns>SqlDataReader</returns>
         public static SqlDataReader ExecuteReader(string strSQL)
         {
             SqlConnection connection = new SqlConnection(connectionString);
             SqlCommand cmd = new SqlCommand(strSQL, connection);
             try
             {
                 connection.Open();
                 SqlDataReader myReader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                 return myReader;
             }
             catch (System.Data.SqlClient.SqlException e)
             {
                 throw e;
             }   

         }

2、三层DAL层方法

 /// <summary>
         /// 把读出的数据转换成List
         /// </summary>
         public List<int> GetUserList(int hid)
         {
             string sql = " select V_UserID from UserVoters where V_HeadlineID=" + hid + "";
             SqlDataReader dr = DbHelperSQL.ExecuteReader(sql);
             List<UserVotersModel> plist = new List<UserVotersModel>();
             while (dr.Read())
             {
                 UserVotersModel uvm = new UserVotersModel();
                 uvm.V_UserID = int.Parse(dr["V_UserID"].ToString());
                 plist.Add(uvm);
             }
             List<int> list = new List<int>();
             for (int i = ; i < plist.Count; i++)
             {
                 list.Add(int.Parse(plist[i].V_UserID.ToString()));
             }
             return list;
         }

3、把List当参数放到sql语句里的方法

  /// <summary>
         /// 获得未投票用户列表
         /// </summary>
         public DataSet GetNoPersonList(List<int> list)
         {
             StringBuilder strSql = new StringBuilder();
             if (list != null && list.Count > )
             {
                 string listMes = string.Empty;
                 foreach (int str in list)
                 {
                     listMes += "'" + str + "',";
                 }
                 strSql.Append("select U_Uid,U_Name,U_Sex,U_Phone,U_QQ  from dbo.UsersInfo where U_ID not in(" + listMes.TrimEnd(',') + ") and U_Level=4 and U_Name='' ORDER BY  U_ID DESC ");
                 return DbHelperSQL.Query(strSql.ToString());
             }
             else
             {
                 strSql.Append(" select U_Uid,U_Name,U_Sex,U_Phone,U_QQ  from dbo.UsersInfo where U_Level=4 and  U_Name='' ORDER BY  U_ID DESC ");
                 return DbHelperSQL.Query(strSql.ToString());
             }
         }

二、没有帮助类直接读取数据库

 /// <summary>
         /// 读取数据库的信息,并转换成List
         /// </summary>
         public List<MailData> GetExpiredLicense()
         {
             string connectionString = "Data Source=01;Initial Catalog=Music;Persist Security Info=True;User ID=Musicname;Password=123456";
             SqlConnection conn = new SqlConnection(connectionString);
             conn.Open();
             string sql = string.Format( @" select * from Tale" );

             SqlDataAdapter da = new SqlDataAdapter(sql, connectionString);
             DataSet ds = new DataSet();
             da.Fill(ds);
             List<MailData> list = new List<MailData>(); //MailData为要查询表的实体类
             foreach (DataRow item in ds.Tables[].Rows)
             {
                 list.Add(MailData.ConvertRow(item));
             }
             return list;
         }