在Models文件夹下添加一个User类:
namespace MyFirstApp.Models { public class User { public int ID { get; set; } public string Name { get; set; } public string Email { get; set; } public string Bio { get; set; }
}
}
除了你期望的用来构建Movie模型的属性外,将作为数据库主键的ID字段是必须的。
安装Entity Framework Core MySQL相关依赖项
注:其中"MySql.Data.EntityFrameworkCore": "7.0.6-ir31",要7.0.6以上版本。
Missing implementation for running EntityFramework Core code first migration。
创建Entity Framework Context数据库上下文
在Models文件夹下添加一个UserContext类:
/// <summary> /// The entity framework context with a User DbSet /// > dotnet ef migrations add MyMigration /// </summary> public class UserContext : DbContext { public DbSet<User> Users { get; set; } protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) { var builder = new ConfigurationBuilder()
.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true); var configuration = builder.Build(); string connectionString = configuration.GetConnectionString("MyConnection");
optionsBuilder.UseMySQL(connectionString);
} protected override void OnModelCreating(ModelBuilder builder) {
builder.Entity<User>().HasKey(m => m.ID); base.OnModelCreating(builder);
}
}
OnConfiguring方法里面的指定使用MySQL provider及具体的连接字符串等逻辑也可以统一放到Startup类中的ConfigureServices方法中:
public void ConfigureServices(IServiceCollection services) { string connectionString = Configuration.GetConnectionString("MyConnection");
services.AddDbContext<UserContext>(options =>
options.UseMySQL(connectionString)
); // Add framework services. services.AddMvc();
}
注:UseMySQL是MySQL.Data.EntityFrameworkCore.Extensions里面的一个扩展方法,所以要手动添加using MySQL.Data.EntityFrameworkCore.Extensions;命名空间。这个小问题也花费了我不少的时间和精力。
创建数据库
通过Migrations工具来创建数据库。
运行dotnet ef migrations add MyMigration Entity Framework .NET Core CLI Migrations命令来创建一个初始化迁移命令。
运行dotnet ef database update应用一个你所创建的新的迁移到数据库。因为你的数据库还没不存在,它会在迁移被应用之前为你创建所需的数据库。
然后就会在项目生成Migrations文件夹,包括20161121064725_MyMigration.cs、20161121064725_MyMigration.Designer、UserContextModelSnapshot这样的文件:
20161121064725_MyMigration.Designer.cs类:
[DbContext(typeof(UserContext))]
[Migration("20161121064725_MyMigration")] partial class MyMigration { protected override void BuildTargetModel(ModelBuilder modelBuilder) {
modelBuilder
.HasAnnotation("ProductVersion", "1.0.0-rtm-21431");
modelBuilder.Entity("MyFirstApp.Models.User", b =>
{
b.Property<int>("ID")
.ValueGeneratedOnAdd();
b.Property<string>("Bio");
b.Property<string>("Email");
b.Property<string>("Name");
b.HasKey("ID");
b.ToTable("Users");
});
}
}
20161121064725_MyMigration.cs Partial类:
public partial class MyMigration : Migration { protected override void Up(MigrationBuilder migrationBuilder) {
migrationBuilder.CreateTable(
name: "Users",
columns: table => new {
ID = table.Column<int>(nullable: false)
.Annotation("MySQL:AutoIncrement", true),
Bio = table.Column<string>(nullable: true),
Email = table.Column<string>(nullable: true),
Name = table.Column<string>(nullable: true)
},
constraints: table =>
{
table.PrimaryKey("PK_Users", x => x.ID);
});
} protected override void Down(MigrationBuilder migrationBuilder) {
migrationBuilder.DropTable(
name: "Users");
}
}
UserContextModelSnapshot类:
[DbContext(typeof(UserContext))] partial class UserContextModelSnapshot : ModelSnapshot { protected override void BuildModel(ModelBuilder modelBuilder) {
modelBuilder
.HasAnnotation("ProductVersion", "1.0.0-rtm-21431");
modelBuilder.Entity("MyFirstApp.Models.User", b =>
{
b.Property<int>("ID")
.ValueGeneratedOnAdd();
b.Property<string>("Bio");
b.Property<string>("Email");
b.Property<string>("Name");
b.HasKey("ID");
b.ToTable("Users");
});
}
}
新创建的数据库结构如下:
将上述的Migrations文件夹中的代码与MySQL数据库表__EFMigrationsHistory对照一下,你会发现该表是用来跟踪记录实际已经应用到数据库的迁移信息。
创建User实例并将实例保存到数据库
public class Program { public static void Main(string[] args) { using (var db = new UserContext())
{
db.Users.Add(new User { Name = "Charlie Chu", Email = "charlie.thinker@aliyun.com", Bio = "I am Chalrie Chu." }); var count = db.SaveChanges();
Console.WriteLine("{0} records saved to database", count);
Console.WriteLine();
Console.WriteLine("All users in database:"); foreach (var user in db.Users)
{
Console.WriteLine(" - {0}", user.Name);
}
}
}
}