說明

此例篩選了感興趣及常用部分

參考文獻

https://docs.microsoft.com/en-us/ef/core/modeling/relationships

One to Many

Many to Many

新增一個中間類，再轉換成One to Many及One to Many的形式

class MyContext : DbContext
{
    public DbSet<Post> Posts { get; set; }
    public DbSet<Tag> Tags { get; set; }

    protected override void
 
 OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<PostTag>()
            .HasKey(t => new { t.PostId, t.TagId });

        modelBuilder.Entity<PostTag>()
            .HasOne(pt => pt.Post)
            .WithMany(p => p.PostTags)
            .HasForeignKey(pt 
 
=> pt.PostId);

        modelBuilder.Entity<PostTag>()
            .HasOne(pt => pt.Tag)
            .WithMany(t => t.PostTags)
            .HasForeignKey(pt => pt.TagId);
    }
}

public class Post
{
    public int PostId { get; set; }
    public string Title { get; set; }
    public
 
 string Content { get; set; }

    public List<PostTag> PostTags { get; set; }
}

public class Tag
{
    public string TagId { get; set; }

    public List<PostTag> PostTags { get; set; }
}

public class PostTag
{
    public int PostId { get; set; }
    public Post Post { get; set; }

    public string TagId { get; set; }
    public Tag Tag { get; set; }
}

One to One（One to Zero)

class MyContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }
    public DbSet<BlogImage> BlogImages { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Blog>()
            .HasOne(p => p.BlogImage)
            .WithOne(i => i.Blog)
            .HasForeignKey<BlogImage>(b => b.BlogForeignKey);
    }
}

public class Blog
{
    public int BlogId { get; set; }
    public string Url { get; set; }

    public BlogImage BlogImage { get; set; }
}

public class BlogImage
{
    public int BlogImageId { get; set; }
    public byte[] Image { get; set; }
    public string Caption { get; set; }

    public int BlogForeignKey { get; set; }
    public Blog Blog { get; set; }
}

使用Migraion

將Model模型放在單獨的類庫中

使用CLI commands

需要在此類庫中安裝Migration必須的Nuget包，編輯.csproj

<ItemGroup>
  <DotNetCliToolReference Include="Microsoft.EntityFrameworkCore.Tools.DotNet" Version="2.0.0" />
  <DotNetCliToolReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Tools" Version="2.0.0" />
</ItemGroup>

MSSql Server

dotnet ef migrations add Initial -c SchoolContext -o Data/SqlServerMigrations -s ../RelationshipStudy

dotnet ef database update -s ../RelationshipStudy

dotnet ef migrations remove -c SchoolContext -s ../RelationshipStudy

Entity Framework Core Relationship的學習筆記