ASP.NET Core 入門教程八、ASP.NET Core + Entity Framework Core 數據訪問入門

時間 2019-12-10

標籤 asp.net asp core 入門教程 entity framework 數據訪問欄目 ASP 简体版

原文原文鏈接

1、前言

一、本教程主要內容

ASP.NET Core MVC 集成 EF Core 介紹&操做步驟
ASP.NET Core MVC 使用 EF Core + Linq to Entity 訪問MySQL數據庫
ASP.NET Core MVC 使用 EF Core + 原生SQL訪問MySql數據庫
EF Core + MySQL數據庫插入數據後獲取自增列的值

Entity Framework Core 簡稱爲 EF Core

二、本教程環境信息

軟件/環境	說明
操做系統	Windows 10
SDK	2.1.401
ASP.NET Core	2.1.3
MySQL	8.0.x
IDE	Visual Studio Code 1.30
瀏覽器	Chrome 70

VS Code插件	版本	說明
C#	1.17.1	提供C#智能感知， .NET Core 調試、編譯等
vscdoe-solution-explorer	0.3.1	提供解決方案視圖

本篇代碼如下代碼進行調整：https://github.com/ken-io/asp...mysql

三、準備工做

安裝MySQL數據庫：https://dev.mysql.com/downloa...git

Windows環境

下載安裝包後雙擊安裝，一直下一步便可。github

MacOS環境

參考：https://ken.io/note/macos-mys...sql

CentOS環境

參考：https://ken.io/note/centos-my...數據庫

四、前置知識

控制反轉（IOC）原則與依賴注入（DI）

ASP.NET Core 默認集成了DI。全部官方模塊的引入都要使用DI的方式引入。macos

https://baike.baidu.com/item/IOCjson

Linq使用教程

https://docs.microsoft.com/zh...centos

2、EF Core + MySQL 前置準備

EF Core 全稱：Entity Framework Core，爲微軟爲 .NET Core平臺開發的ORM框架。對應是 .NET Framework平臺的 Entity Framework（EF），不管是EF仍是EF Core均可以說是 .NET 平臺開發效率最高的ORM框架。瀏覽器

一、引入 EF Core + MySQL Provider

EF Core已經集成在 ASP.NET Core 中，但默認並不支持MySQL，若是須要鏈接MySQL,須要添加MySQL相關的Provider，這裏我選擇的是：Pomelo.EntityFrameworkCore.MySqlbash

任意命令行操做便可，我用的是VS Code自帶的命令行

//進入項目根目錄： Ken.Tutorial.Web
cd Ken.Tutorial.Web

//添加Package
dotnet add package Pomelo.EntityFrameworkCore.MySql

這裏我添加的 MySql.Data.EntityFrameworkCore 版本是 8.0.13，若是你想跟我使用同樣的版本，可使用如下命令：

dotnet add package Pomelo.EntityFrameworkCore.MySql --version 2.1.4

二、建立MySQL庫表

建立數據庫

CREATE DATABASE ken_tutorial;

建立表

USE ken_tutorial;

DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) DEFAULT NULL,
  `age` int(11) DEFAULT NULL,
  `hobby` varchar(500) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

三、配置連接字符串

在項目根目錄Ken.Tutorial.Web中建立配置文件appsettings.json,並寫入如下配置

{
  "ConnectionStrings": {
    "testdb": "server=localhost;database=Ken.Tutorial;uid=root;pwd=root;"
  }
}

四、實體&DbContext準備

建立user表對應實體

在項目根目錄Ken.Tutorial.Web中建立目錄Models,並在其中建立類：UserEntity.cs

using System;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace Ken.Tutorial.Web.Models
{
    [Table("user")]
    [Serializable]
    public class UserEntity
    {
        [Key]//主鍵
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]//自增列
        [Column("id")]
        public int Id { get; set; }

        [Column("name")]
        public string Name { get; set; }

        [Column("age")]
        public int Age { get; set; }

        [Column("hobby")]
        public string Hobby { get; set; }
    }
}

建立DBContext

在項目根目錄Ken.Tutorial.Web中建立目錄Repositories,並在其中建立類：TutorialDbContext.cs

using System;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;

namespace Ken.Tutorial.Web.Repositories
{
    public class TutorialDbContext : DbContext
    {
        private IConfiguration Configuration { get; }

        public TutorialDbContext(IConfiguration configuration)
        {
            this.Configuration = configuration;
        }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseMySql(Configuration.GetConnectionString("testdb"));
        }
        
        ppublic DbSet<UserEntity> Users { get; set; }
    }
}

TutorialDbContext 繼承了 DbContext，而後再Context初始化時配置MySQL連接。

因爲 ASP.NET Core 默認使用了DI組件，因此咱們取配置文件，就須要在構造函數中獲取 IConfiguration 注入的實例。

在Startup.cs配置注入，以便數據訪問類能夠訪問DI方式獲取TutorialDbContext

public void ConfigureServices(IServiceCollection services)
{
    //引入MVC模塊
    services.AddMvc();

    //配置DbContext注入
    services.AddTransient<TutorialDbContext>();
}

3、EF Core + Linq to entity 訪問數據庫

一、建立Linq To Entity 數據訪問類

using System;
using System.Collections.Generic;
using System.Linq;
using Ken.Tutorial.Web.Models;

namespace Ken.Tutorial.Web.Repositories
{
    public class TutorialRepository
    {
        private TutorialDbContext DbContext { get; }

        public TutorialRepository(TutorialDbContext dbContext)
        {
            //在構造函數中注入DbContext
            this.DbContext = dbContext;
        }

        //添加
        public int Add(UserEntity user)
        {
            using (DbContext)
            {
                //因爲咱們在UserEntity.Id配置了自增列的Attribute，EF執行完成後會自動把自增列的值賦值給user.Id
                DbContext.Users.Add(user);
                return DbContext.SaveChanges();
            }

        }

        //刪除
        public int Delete(int id)
        {
            using (DbContext)
            {
                var userFromContext = DbContext.Users.FirstOrDefault(u => u.Id == id);
                DbContext.Users.Remove(userFromContext);
                return DbContext.SaveChanges();
            }
        }

        //更新
        public int Update(UserEntity user)
        {
            using (DbContext)
            {
                var userFromContext = DbContext.Users.FirstOrDefault(u => u.Id == user.Id);
                userFromContext.Name = user.Name;
                userFromContext.Age = user.Age;
                userFromContext.Hobby = user.Hobby;
                return DbContext.SaveChanges();
            }
        }

        //查詢
        public UserEntity QueryById(int id)
        {
            using (DbContext)
            {
                return DbContext.Users.FirstOrDefault(u => u.Id == id);
            }
        }

        //查詢集合
        public List<UserEntity> QueryByAge(int age)
        {
            using (DbContext)
            {
                return DbContext.Users.Where(u => u.Age == age).ToList();
            }
        }

        //查看指定列
        public List<string> QueryNameByAge(int age)
        {
            using (DbContext)
            {
                return DbContext.Users.Where(u => u.Age == age).Select(u => u.Name).ToList();
            }
        }

        //分頁查詢
        public List<UserEntity> QueryUserPaging(int pageSize, int page)
        {
            using (DbContext)
            {
                return DbContext.Users.Skip(pageSize * (page - 1)).Take(pageSize).ToList();
            }
        }

        //事務：將年齡<0的用戶修改年齡爲0
        public int FixAge()
        {
            using (DbContext)
            {
                using (var transaction = DbContext.Database.BeginTransaction())
                {
                    try
                    {
                        var userListFromContext = DbContext.Users.Where(u => u.Age < 0);
                        foreach (UserEntity u in userListFromContext)
                        {
                            u.Age = 0;
                        }
                        var count = DbContext.SaveChanges();
                        transaction.Commit();
                        return count;
                    }
                    catch
                    {
                        transaction.Rollback();
                        return 0;
                    }
                }
            }
        }
    }
}

二、建立測試API

在Controllers文件夾下建立EfCoreController.cs做爲訪問入口

using System;
using Ken.Tutorial.Web.Models;
using Ken.Tutorial.Web.Repositories;
using Microsoft.AspNetCore.Mvc;

namespace Ken.Tutorial.Web.Controllers
{
    public class EfCoreController : Controller
    {
        public TutorialRepository Repository { get; }

        public EfCoreController(TutorialRepository repository)
        {
            this.Repository = repository;
        }

        public IActionResult Add(UserEntity user)
        {
            var message = Repository.Add(user) > 0 ? "success" : "failed";
            return Json(new { Message = message, User = user });
        }

        public IActionResult Delete(int id)
        {
            var message = Repository.Delete(id) > 0 ? "success" : "failed";
            return Json(new { Message = message });
        }

        public IActionResult Update(UserEntity user)
        {
            var message = Repository.Update(user) > 0 ? "success" : "failed";
            return Json(new { Message = message, User = user });
        }

        public IActionResult QueryById(int id)
        {
            var user = Repository.QueryById(id);
            return Json(new { User = user });
        }

        public IActionResult QueryByAge(int age)
        {
            var users = Repository.QueryByAge(age);
            return Json(new { Users = users });
        }

        public IActionResult QueryNameByAge(int age)
        {
            var users = Repository.QueryNameByAge(age);
            return Json(new { Users = users });
        }

        public IActionResult QueryUserPaging(int pageSize, int page)
        {
            var users = Repository.QueryUserPaging(pageSize, page);
            return Json(new { Users = users });
        }

        public IActionResult FixAge()
        {
            var count = Repository.FixAge();
            return Json(new { FixCount = count });
        }

    }
}

三、啓動測試

在Startup.cs中配置Repository注入

public void ConfigureServices(IServiceCollection services)
{
    //其餘代碼省略

    //配置Repository注入
    services.AddTransient<TutorialRepository>();
}

啓動項目並測試

API	示例
添加用戶	/efcore/add?name=ken&age=18&hobby=coding
刪除用戶	/efcore/delete?id=0
更新用戶	/efcore/update?id=1&name=ken&age=666&hobby=codingOrGaming
查詢單個用戶	/efcore/querybyid?id=0
查詢多個用戶	/efcore/querybyage?age=18
查詢多個用戶名	/efcore/querynamebyage?age=18
分頁查詢用戶	/efcore/queryuserpaging?pagesize=3&page=1
修復異常年齡	/efcore/fixage

4、EF Core + 原生SQL 訪問數據庫

一、建立EF Core + 原生SQL 數據訪問類

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using Ken.Tutorial.Web.Models;
using Microsoft.EntityFrameworkCore;
using MySql.Data.MySqlClient;

namespace Ken.Tutorial.Web.Repositories
{
    public class TutorialWithSqlRepository
    {
        private TutorialDbContext DbContext { get; }

        public TutorialWithSqlRepository(TutorialDbContext dbContext)
        {
            //在構造函數中注入DbContext
            this.DbContext = dbContext;
        }

        //添加
        public int Add(UserEntity user)
        {
            using (var connection = DbContext.Database.GetDbConnection())
            {
                connection.Open();
                var command = connection.CreateCommand() as MySqlCommand;
                command.CommandText = "INSERT INTO user (name,age,hobby) VALUES(@name,@age,@hobby)";
                command.Parameters.Add(new MySqlParameter()
                {
                    ParameterName = "@name",
                    DbType = DbType.String,
                    Value = user.Name
                });
                command.Parameters.Add(new MySqlParameter()
                {
                    ParameterName = "@age",
                    DbType = DbType.Int32,
                    Value = user.Age
                });
                command.Parameters.Add(new MySqlParameter()
                {
                    ParameterName = "@hobby",
                    DbType = DbType.String,
                    Value = user.Hobby
                });
                var count = command.ExecuteNonQuery();
                //獲取插入時產生的自增列Id並賦值給user.Id使用
                user.Id = (int)command.LastInsertedId;
                return count;
            }

        }

        //刪除
        public int Delete(int id)
        {
            using (DbContext)
            {
                return DbContext.Database.ExecuteSqlCommand(
                    "DELETE FROM user WHERE id={0}", id);
            }
        }

        //更新
        public int Update(UserEntity user)
        {
            using (DbContext)
            {
                return DbContext.Database.ExecuteSqlCommand(
                     "UPDATE user SET name={0}, age={1}, hobby={2} WHERE id={3}",
                      user.Name, user.Age, user.Hobby, user.Id);
            }
        }

        //查詢
        public UserEntity QueryById(int id)
        {
            using (DbContext)
            {
                return DbContext.Users.FromSql("SELECT id,name,age,hobby FROM user WHERE id={0}", id).FirstOrDefault();
            }
        }

        //查詢集合
        public List<UserEntity> QueryByAge(int age)
        {
            using (DbContext)
            {
                return DbContext.Users.FromSql("SELECT id,name,age,hobby FROM user WHERE age={0}", age).ToList();
            }
        }

        //查看指定列
        public List<string> QueryNameByAge(int age)
        {
            using (DbContext)
            {
                return DbContext.Users.FromSql("SELECT id,name FROM user WHERE age={0}", age).Select(u => u.Name).ToList();
            }
        }

        //分頁查詢
        public List<UserEntity> QueryUserPaging(int pageSize, int page)
        {
            using (DbContext)
            {
                return DbContext.Users.FromSql("SELECT id,name,age,hobby FROM user LIMIT {0},{1}", pageSize * (page - 1), pageSize).ToList();
            }
        }

        //事務：將年齡<0的用戶修改年齡爲0
        public int FixAge()
        {
            using (DbContext)
            {
                using (var connection = DbContext.Database.GetDbConnection())
                {
                    //打開鏈接
                    connection.Open();
                    //開啓事務
                    using (var transaction = connection.BeginTransaction())
                    {
                        try
                        {
                            //獲取命令對象
                            var command = connection.CreateCommand();
                            command.Transaction = transaction;
                            command.CommandText = "UPDATE user SET age=@age WHERE age<@age";
                            command.Parameters.Add(new MySqlParameter()
                            {
                                ParameterName = "@age",
                                DbType = DbType.Int32,
                                Value = 0
                            });
                            var count = command.ExecuteNonQuery();
                            transaction.Commit();
                            return count;
                        }
                        catch (Exception ex)
                        {
                            connection.Close();
                            transaction.Rollback();
                            return 0;
                        }
                    }

                }
            }
        }
    }
}

二、建立測試API

在Controllers文件夾下建立EfCoreWithSqlController.cs做爲訪問入口

using System;
using Ken.Tutorial.Web.Models;
using Ken.Tutorial.Web.Repositories;
using Microsoft.AspNetCore.Mvc;

namespace Ken.Tutorial.Web.Controllers
{
    public class EfCoreWithSqlController : Controller
    {
        public TutorialWithSqlRepository Repository { get; }

        public EfCoreWithSqlController(TutorialWithSqlRepository repository)
        {
            this.Repository = repository;
        }

        public IActionResult Add(UserEntity user)
        {
            var message = Repository.Add(user) > 0 ? "success" : "failed";
            return Json(new { Message = message, User = user });
        }

        public IActionResult Delete(int id)
        {
            var message = Repository.Delete(id) > 0 ? "success" : "failed";
            return Json(new { Message = message });
        }

        public IActionResult Update(UserEntity user)
        {
            var message = Repository.Update(user) > 0 ? "success" : "failed";
            return Json(new { Message = message, User = user });
        }

        public IActionResult QueryById(int id)
        {
            var user = Repository.QueryById(id);
            return Json(new { User = user });
        }

        public IActionResult QueryByAge(int age)
        {
            var users = Repository.QueryByAge(age);
            return Json(new { Users = users });
        }

        public IActionResult QueryNameByAge(int age)
        {
            var users = Repository.QueryNameByAge(age);
            return Json(new { Users = users });
        }

        public IActionResult QueryUserPaging(int pageSize, int page)
        {
            var users = Repository.QueryUserPaging(pageSize, page);
            return Json(new { Users = users });
        }

        public IActionResult FixAge()
        {
            var count = Repository.FixAge();
            return Json(new { FixCount = count });
        }

    }
}

三、啓動測試

在Startup.cs中配置Repository注入

public void ConfigureServices(IServiceCollection services)
{
    //其餘代碼省略

    //配置Repository注入
    services.AddTransient<TutorialWithSqlRepository>();
}

啓動項目並測試

API	示例
添加用戶	/efcorewithsql/add?name=ken&age=18&hobby=coding
刪除用戶	/efcorewithsql/delete?id=0
更新用戶	/efcorewithsql/update?id=1&name=ken&age=666&hobby=codingOrGaming
查詢單個用戶	/efcorewithsql/querybyid?id=0
查詢多個用戶	/efcorewithsql/querybyage?age=18
查詢多個用戶名	/efcorewithsql/querynamebyage?age=18
分頁查詢用戶	/efcorewithsql/queryuserpaging?pagesize=3&page=1
修復異常年齡	/efcorewithsql/fixage