三层常用就是UI,DAL,MODEL 还有其他的比如接口 模式等 这里以普通三层为例 实现插入数据的功能 。

先定义model实体类

private int uid; private string uname; private string upass; public int UserId        {
    get { return uid; } set { uid = value; }        } public string UserName        {
    get { return uname; } set { uname = value; }        } public string UserPass        {
    get { return upass; } set { upass = value; }        }

DAL数据访问层；

public UserService()        {        }        private string db = System.Configuration.ConfigurationSettings.AppSettings["ConstrSQL"].ToString();//数据库连接字符串        /// 
        /// 执行数据插入        /// 
        ///         /// 
             public bool Insert(Model.UserInfo model)        {            using (SqlConnection conn = new SqlConnection())            {                conn.ConnectionString = db;                conn.Open();                string strsql = "insert into UserInfos(UserName,UserPass)values(@uname,@upass)";                SqlCommand cmd = new SqlCommand(strsql, conn);                cmd.Parameters.Add("@uname", SqlDbType.VarChar, 50);                cmd.Parameters.Add("@upass", SqlDbType.VarChar, 50);                cmd.Parameters["@uname"].Value = model.UserName;                cmd.Parameters["@upass"].Value = model.UserPass;                if (cmd.ExecuteNonQuery() > 0)                {                    return true;                }                else                {                    return false;                }                conn.Dispose();                conn.Close();            }        }

 BLL层我的理解就是UI与DAL之间的桥梁 ，主要是一调用的函数（方法）

public bool BLL_Insert(Model.UserInfo mu)        {
               DAL.UserService du = new DAL.UserService(); return du.Insert(mu);        }

 UI层调用BLL

1 Model.UserInfo mu = new Model.UserInfo(); 2         mu.UserName = TextBox1.Text; 3         mu.UserPass = TextBox2.Text; 4         DAL.UserService du = new DAL.UserService(); 5         du.Insert(mu); 6         Response.Write("提交成功！"); 7         TextBox2.Text = "";

三层顺序model -dal-bll，BLL引用DAL，DAL引用MODEL