11.16三层架构

 

1.查询

进行模糊查询要将%%号写在SqlParameter 实例中，写法为

SqlParameter sqlParameters = new SqlParameter("@name",$"%{name}%");
SQL语句中不需要添加%%，也不用加引号，加@即可，

　　　　　　　 var sql = "select * from ClassInfo where name like @name";

            SqlParameter sqlParameters = new SqlParameter("@name",$"%{name}%");

            DataTable table = SqlHelper.Query(sql,sqlParameters);

            List<ClassInfo> list = new List<ClassInfo>();

            foreach (DataRow row in table.Rows)
            {
                var cls = new ClassInfo()
                {
                    Id = Convert.ToInt32(row["Id"]),
                    Name=Convert.ToString(row["Name"]),
                    Comment=Convert.ToString(row["Comment"])
                };
                list.Add(cls);
            }
            return list;
        }

2.根据ID查询 

            SqlParameter[] sqlParameters = new SqlParameter[]
            {
            new SqlParameter("@id",id)
            };

            SqlDataReader reader = SqlHelper.Reader(sql, sqlParameters);

            ClassInfo info = null;

            if (reader.Read())

            {
                info = new ClassInfo()
                {
                    Id = Convert.ToInt32(reader["Id"]),
                    Name = Convert.ToString(reader["Name"]),
                    Comment = Convert.ToString(reader["Comment"])
                };
            }
            reader.Close();
            return info;
        }

3.BLL层只需要调用DAL层方法即可

 public static List<ClassInfo> Select(string name="") {
            return ClassInfoDAL.Select(name);
        
        }

        public static ClassInfo Select(int id) {
            return ClassInfoDAL.Select(id);
        }

4.在UI层绑定BLL层方法，并绑定到Gridview中。

用DataSource引用BLL层方法，再用DataBind()绑定到Gridview.

5.AutoGenerateColumns="False"为取消自动添加列