本文主要介绍在.NET Core环境下,通过donet命令,使用Code First方式,用EF Core(Entity Framework Core) 创建生成数据库方法示例代码。Code First方法使您能够在代码中定义实体模型,从模型创建数据库,然后将数据添加到数据库。应用程序添加的数据也由应用程序使用MySQL Connector / NET检索。虽然此示例使用C#语言,但您可以在Windows,macOS或Linux上执行它。

1、为此示例创建一个控制台应用程序

1) 使用.NET Core命令行界面(CLI)初始化有效的.NET Core项目和控制台应用程序,然后切换到新创建的文件夹(mysqlefcore)

dotnet new console –o mysqlefcore
cd mysqlefcore

2) MySql.Data.EntityFrameworkCore 使用CLI 将包添加到应用程序

dotnet add package MySql.Data.EntityFrameworkCore --version 6.10.8

或者,您可以使用Visual Studio中的程序包管理器控制台添加程序包:

Install-Package MySql.Data.EntityFrameworkCore -Version 6.10.8

注意
版本(例如6.10.8)必须与您使用的实际Connector / NET版本匹配。有关当前版本信息,请参阅 表9.2“支持的Entity Framework Core版本”

3) 恢复项目文件中指定的依赖项和项目特定工具

dotnet restore

2、创建模型并运行应用程序

控制器应用程序将使用此EF Core示例中的模型。它由两个与书库相关的实体组成,这些实体将在 LibraryContext类(或数据库上下文)中配置。

1) 创建一个名为的新文件LibraryModel.cs ,然后将以下Book和 Publisher类添加到 mysqlefcore命名空间

namespace mysqlefcore
{
public class Book
{
public string ISBN { get; set; }
public string Title { get; set; }
public string Author { get; set; }
public string Language { get; set; }
public int Pages { get; set; }
public virtual Publisher Publisher { get; set; }
}
public class Publisher
{
public int ID { get; set; }
public string Name { get; set; }
public virtual ICollection<Book> Books { get; set; }
}
}

2) 创建一个名为的新文件LibraryContext.cs并添加后面的代码。将通用连接字符串替换为适合MySQL服务器配置的字符串

该LibraryContext class 实体使用,它使模型的特定属性,如Key,所需的列,引用等的配置。

using Microsoft.EntityFrameworkCore;
using MySQL.Data.EntityFrameworkCore.Extensions;
namespace mysqlefcore
{
public class LibraryContext : DbContext
{
public DbSet<Book> Book { get; set; }
public DbSet<Publisher> Publisher { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseMySQL("server=localhost;database=library;user=user;password=password");
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<Publisher>(entity =>
{
entity.HasKey(e => e.ID);
entity.Property(e => e.Name).IsRequired();
});
modelBuilder.Entity<Book>(entity =>
{
entity.HasKey(e => e.ISBN);
entity.Property(e => e.Title).IsRequired();
entity.HasOne(d => d.Publisher)
.WithMany(p => p.Books);
});
}
}
}

3) 将以下代码插入现有 Program.cs文件,替换默认的C#代码

using Microsoft.EntityFrameworkCore;
using System;
using System.Text;
namespace mysqlefcore
{
  class Program
  {
    static void Main(string[] args)
    {
      InsertData();
      PrintData();
    }
    private static void InsertData()
    {
      using(var context = new LibraryContext())
      {
        // Creates the database if not exists
        context.Database.EnsureCreated();
        // Adds a publisher
        var publisher = new Publisher
        {
          Name = "Mariner Books"
        };
        context.Publisher.Add(publisher);
        // Adds some books
        context.Book.Add(new Book
        {
          ISBN = "978-0544003415",
          Title = "The Lord of the Rings",
          Author = "J.R.R. Tolkien",
          Language = "English",
          Pages = 1216,
          Publisher = publisher
        });
        context.Book.Add(new Book
        {
          ISBN = "978-0547247762",
          Title = "The Sealed Letter",
          Author = "Emma Donoghue",
          Language = "English",
          Pages = 416,
          Publisher = publisher
        });
        // Saves changes
        context.SaveChanges();
      }
    }
    private static void PrintData()
    {
      // Gets and prints all books in database
      using (var context = new LibraryContext())
      {
        var books = context.Book
          .Include(p => p.Publisher);
        foreach(var book in books)
        {
          var data = new StringBuilder();
          data.AppendLine($"ISBN: {book.ISBN}");
          data.AppendLine($"Title: {book.Title}");
          data.AppendLine($"Publisher: {book.Publisher.Name}");
          Console.WriteLine(data.ToString());
        }
      }
    }
  }
}

4) 使用以下CLI命令还原依赖项,然后运行该应用程序

dotnet restore
dotnet run

运行应用程序的输出

ISBN: 978-0544003415
Title: The Lord of the Rings
Publisher: Mariner Books
ISBN: 978-0547247762
Title: The Sealed Letter
Publisher: Mariner Books

参考文档https://dev.mysql.com/doc/connector-net/en/connector-net-entityframework-core-example.html