Dapper学习笔记（3）-增、删、改、查

一、建表

在数据库中建立如下三张表：

CREATE TABLE [dbo].[T_User]
(
    [UserId]           [int] IDENTITY(1, 1) PRIMARY KEY NOT NULL,
    [Username]         [nvarchar](256) NOT NULL,
    [Password]         [nvarchar](500) NULL,
    [Email]            [nvarchar](256) NULL,
    [PhoneNumber]      [nvarchar](30) NULL,
)

CREATE TABLE [dbo].[T_Role]
(
    [RoleId]           [int] IDENTITY(1, 1) PRIMARY KEY NOT NULL,
    [RoleName]         [nvarchar](256) NOT NULL,
)

CREATE TABLE [dbo].[T_UserRole]
(
     [Id]      [int] IDENTITY(1, 1) PRIMARY KEY NOT NULL,
     [UserId]  [int] FOREIGN KEY REFERENCES [dbo].[T_User] ([UserId]) NOT NULL,
     [RoleId]  [int] FOREIGN KEY REFERENCES [dbo].[T_Role] ([RoleId]) NOT NULL
)

在本篇中只会用到T_Role表，剩下的表在后面的文章中将会涉及到。

二、创建实体类

    public class User
    {
        public User()
        {
            Role = new List<Role>();
        }

        public int UserId { get; set; }
        public string UserName { get; set; }
        public string Password { get; set; }
        public string Email { get; set; }
        public string PhoneNumber { get; set; }
        public List<Role> Role { get; set; }
    }

    public class Role
    {
        public int RoleId { get; set; }
        public string RoleName { get; set; }
    }

在创建实体类时，属性名称一定要与数据库字段一一对应。在本篇中只会用到Role实体类，User实体类在后续文章中会涉及并且会有一定程度上的修改。

三、操作

在进行增、删、改、查操作之前，应先建立与数据库的连接，具体代码如下：

    private static readonly string connectionString = @"Data Source=.;Initial Catalog=test;User Id=sa;Password=sa@126.com";

    private SqlConnection OpenConnection()
    {
        SqlConnection connection = new SqlConnection(connectionString);
        connection.Open();
        return connection;
    }

1、查询实体列表

    private List<Role> QueryRoleData()
    {
        using (IDbConnection con = OpenConnection())
        {
            string query = @"select * from T_Role";
            return con.Query<Role>(query, null).ToList<Role>();
        }
    }

2、添加实体

    private int AddRole()
    {
        using (IDbConnection con = OpenConnection())
        {
            Role role = new Role();
            role.RoleName = "开发人员";
            string strSql = @"insert into T_Role(RoleName)values(@RoleName)";
            int result = con.Execute(strSql, role);
            return result;
        }
    }

3、修改实体

    private int UpdateRole(Role role)
    {
        using (IDbConnection con = OpenConnection())
        {
            role.RoleName = "开发主管";
            string query = "update T_Role set RoleName=@RoleName where RoleId=@RoleId";
            return con.Execute(query, role);
        }
    }

4、删除实体

    private int DeleteRole(Role role)
    {
        using (IDbConnection con = OpenConnection())
        {
            string query = "delete from T_Role where RoleId=@RoleId";
            return con.Execute(query, role);
        }
    }