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);
         }
     }