在数据访问层建一个Server类

using System;
using System.Data;
using System.Configuration;
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.Data.SqlClient;

/// <summary>
///UserServer 的摘要说明
/// </summary>
public class UserServer
{
 public UserServer()
 {
  //
  //TODO: 在此处添加构造函数逻辑
  //
 }

    public static Member GetuserByUserName(string username)
    {
        string sql = "select * from users where username = @username";
        using (SqlDataReader reader = DBHelper.GetReader(sql,new SqlParameter("@username",username)))
        {
            if (reader.Read())
            {
                Member member = new Member();
                member.Username = (string)reader["username"];
                member.Password = (string)reader["password"];
                reader.Close();
                return member;
            }
            else
            {
                reader.Close();
                return null;
            }
        }
    }
}