三层开发体验之数据访问层

这是用实体类型的数组，实体代码为

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Accesscontrol
{
    public class role
    {
        public string  RoleName { get; set; }
        public string  Remark { get; set; }
    }
}

通过传递实体类类型的数组，将实体中的属性值装载到泛型中去 

  public role[] SelectAll()
        {
            using (SqlConnection con = new SqlConnection(constr))
            {
                SqlCommand cmd = con.CreateCommand();
                cmd.CommandText = "select *from role";
                con.Open();
                List<role> roles = new List<role>();
                SqlDataReader sdr = cmd.ExecuteReader();
                while (sdr.Read())
                {
                    role Role = new role();
                    Role.RoleName = sdr.GetString(0);
                    if (!sdr.IsDBNull(1))
                    {
                        Role.Remark = sdr.GetString(1);
                    }
                    roles.Add(Role);
                }
                sdr.Close();
                return roles.ToArray();
            }
        }

接下来是传递泛型的实体类数组，道理和上面的一样

  public List<role> SelectAll()
        {
            using (SqlConnection con = new SqlConnection(constr))
            {
                SqlCommand cmd = con.CreateCommand();
                cmd.CommandText = "select *from role";
                con.Open();
                list<role> lrole=new list<role>();
                role roles = new role();
                SqlDataReader sdr = cmd.ExecuteReader();
                while (sdr.Read())
                {
                    roles.RoleName = sdr.GetString(0);
                    if (!sdr.IsDBNull(1))
                    {
                        roles.Remark = sdr.GetString(1);
                    }
                    lrole.Add(roles);
                }
                sdr.Close();
                return lrole;
            }
        }
 最后这种是直接使用实体类装载

 public role SelectAll()
        {
            using (SqlConnection con = new SqlConnection(constr))
            {
                SqlCommand cmd = con.CreateCommand();
                cmd.CommandText = "select *from role";
                con.Open();
                SqlDataReader sdr = cmd.ExecuteReader();
                while (sdr.Read())
                {
                    role Role = new role();
                    Role.RoleName = sdr.GetString(0);
                    if (!sdr.IsDBNull(1))
                    {
                        Role.Remark = sdr.GetString(1);
                    }
                 }
                sdr.Close();
                return Role;            }
        }