新建.net core webapi项目
在NuGet包管理器中搜索 MySql.Data.EntityFrameworkCore并安装,安装的8.0.14版本,只安装这一个就够了
安装后创建DataContext.cs
using System; using System.Collections.Generic; using System.Linq; using System.Threading.Tasks; using Microsoft.EntityFrameworkCore; namespace WebApplication4 { public class DataContext : DbContext { public DataContext(DbContextOptions<DataContext> options) : base(options) { } public DbSet<TbUser> tbusers { get; set; } protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity<TbUser>(); } } }
TbUser.cs
using System; using System.Collections.Generic; using System.ComponentModel.DataAnnotations.Schema; using System.Linq; using System.Threading.Tasks; namespace WebApplication4 { public class TbUser { [DatabaseGenerated(DatabaseGeneratedOption.None)] public int ID { get; set; } public string NickName { get; set; } public string Email { get; set; } } }
appsettings.json中添加连接字符串
{ "Logging": { "LogLevel": { "Default": "Warning" } }, "ConnectionStrings": { "dbconn": "server=localhost;user id=root;password=root;persistsecurityinfo=True;database=cnis;SslMode=none" }, "AllowedHosts": "*" }
Startup.cs中注入DbContext
public void ConfigureServices(IServiceCollection services) { services.AddDbContext<DataContext>(options => options.UseMySQL(Configuration.GetConnectionString("dbconn"))); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2); }
在Configure方法后面添加DataContext context参数,添加context.Database.EnsureCreated();这样程序运行时,库表不存在的话,会自动创建,不然会报数据库不存在的错误,不用担心DataContext context的传参,该参数会被.net core框架自动注入
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline. public void Configure(IApplicationBuilder app, IHostingEnvironment env, DataContext context) { if (env.IsDevelopment()) { app.UseDeveloperExceptionPage(); } else { // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts. app.UseHsts(); } app.UseHttpsRedirection(); app.UseMvc(); context.Database.EnsureCreated(); }
添加UserController.cs
using System; using System.Collections.Generic; using System.Linq; using System.Threading.Tasks; using Microsoft.AspNetCore.Mvc; namespace WebApplication4.Controllers { [Produces("application/json")] [Route("api/user")] public class UserController: ControllerBase { private readonly DataContext _context; public UserController(DataContext context) { this._context = context; } // POST api/user [HttpPost] public int Post(TbUser user) { _context.Add(user); _context.SaveChanges(); return 200; } // GET api/user [HttpGet] public List<TbUser> Get() { _context.Database.EnsureCreated(); var users = _context.tbusers; List<TbUser> items = new List<TbUser>(); foreach (var item in users) { items.Add(item); } return items; } // GET api/user/5 [HttpGet("{id}")] public TbUser Get(int id) { var u = _context.tbusers.Find(id); return u; } // DELETE api/user/5 [HttpDelete("{id}")] public int Delete(int id) { var u = _context.tbusers.Remove(new TbUser() { ID = id }); _context.SaveChanges(); return 200; } // PUT api/user/5 [HttpPut("{id}")] public int Put(int id, TbUser user) { var u = _context.tbusers.Update(user); _context.SaveChanges(); return 200; } } }
这时运行程序访问系统,就会自动创建库和表,如果需要做数据库迁移,则执行如下命令:
如果用的是vs code,则在终端中执行
dotnet ef migrations add firstMigrations
dotnet ef database update
PS F:projectsmyApiMyApi> dotnet ef migrations add firstMigrations info: Microsoft.EntityFrameworkCore.Infrastructure[10403] Entity Framework Core 2.2.1-servicing-10028 initialized 'DataContext' using provider 'MySql.Data.EntityFrameworkCore' with options: None Done. To undo this action, use 'ef migrations remove'
PS F:projectsmyApiMyApi> dotnet ef database update
Build failed.
PS F:projectsmyApiMyApi>
如果用的是vs,在NuGet程序包管理器控制台中执行迁移命令
Add-Migration FirstMigration
Update-Database
首次进行迁移执行update-database的时候,会报错:
MySql.Data.MySqlClient.MySqlException (0x80004005): Table 'test.__efmigrationshistory' doesn't exit
解决方式是:
手动创建这个 'test.__efmigrationshistory' 表
CREATE TABLE `__EFMigrationsHistory` ( `MigrationId` nvarchar(150) NOT NULL, `ProductVersion` nvarchar(32) NOT NULL, PRIMARY KEY(`MigrationId`) );
然后执行update-database
这样数据迁移就能完成了,表现表已经创建好了,再运行程序
http://localhost:17800/api/user
返回json数据
[{"id":1,"nickName":"张三","email":"123@abc.com"}]