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;            }        }
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