一个简单的三层实现

Model代码

/// <summary>

/// 初始化登录名称、登录密码(Model类)
/// </summary>
       private string adminUser = string.Empty; //设置用户名称为空值
        private string adminPwd = string.Empty; //设置用户密码为空值
        public string AdminUser
        {
            get
            {
                return this.adminUser;
            }
            set
            {
                this.adminUser = value;
            }
        }
        public string AdminPwd
        {
            get
            {
                return this.adminPwd;
            }
            set
            {
                this.adminPwd = value;
            }
        }

BLL层:

         /// <summary>
        /// 用户登录(BLL类)
        /// </summary>
        /// <param name="m"></param>
        /// <returns></returns>
        public static int sysLogin(Model m)
        {
            string str = "adminValid"; //存储过程名称
            SqlParameter[] sqlParameter =
                {
                    //将UI层传递过来的用户名称和密码赋值给存储过程中的变量分别是adminUser和adminPwd(注意大小写)
                    new SqlParameter("adminUser",m.AdminUser),
                    new SqlParameter("adminPwd",m.AdminPwd)
                };
            DAL d = new DAL();
            return Int32.Parse(d.ExecuteScalar(str,sqlParameter));
        }

DAL层：

        /// <summary>
        /// 新建一个SQL登录链接
        /// </summary>
        /// <returns></returns>
        private static SqlConnection con()
        {
            return new SqlConnection("Data Source=localhost;Initial Catalog=数据库名称;Integrated Security=SSPI;");
        }
        /// <summary>
        /// 执行操作(DAL类)
        /// </summary>
        /// <param name="str"></param>
        /// <param name="sql"></param>
        /// <returns></returns>
        public string ExecuteScalar(string str, SqlParameter[] sql)
        {
            SqlConnection con = DAL.con();
            try
            {
                con.Open();
                SqlCommand com = new SqlCommand(str, con);
                com.CommandType = CommandType.StoredProcedure;
                com.Parameters.AddRange(sql);
                return Convert.ToString(com.ExecuteScalar()); //返回受影响的行数(例如影响的行数为1，那么返回数值1到BLL层,然后BLL层将数值1返回到UI层)
            }
            catch (Exception Error)
            {
                throw Error;
            }
            finally
            {
                con.Close();
            }
        }

UI层：

         //UI层
        Model m = new Model(); //实例化Model类
        m.AdminUser = this.TextBox1.Text.ToString(); //将文本框1中的值传递给Model类中的AdminUser
        m.AdminPwd = this.TextBox2.Text.ToString(); //将文本框2中的值传递给Model类中的AdminPwd
        if (BLL.sysLogin(m) > 0)
        {
            this.Label1.Text = "登录成功！马上进入管理平台．．．";
        }
        else
        {
            this.Label1.Text = "用户或密码错误，请重新输入！";
        }

存储过程：

--存储过程(SQL2005)
set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go

ALTER PROC [dbo].[adminValid]
@adminUser varchar(20),@adminPwd varchar(120)
AS
SELECT COUNT(*) FROM admin WHERE adminUser = @adminUser AND adminPwd = @adminPwd