C#•16mo ago

❔ Initializing a relation in Entity Framework Core?

public class Post : Model
{
    public string Slug { get; set; }
    public string? Name { get; set; }
    public string? Content { get; set; }
    public bool Draft { get; set; } = true;
    public DateTime PublishedAt { get; set; } = DateTime.Now;

    public User User { get; set; }
    public Blog Blog { get; set; }
    public ICollection<Comment>? Comments { get; set; }
    public ICollection<Label>? Labels { get; set; }

    public Post(string slug, string? name, string? content) : base()
    {
        Slug = slug;
        Name = name;
        Content = content;
    }
}

public class Post : Model
{
    public string Slug { get; set; }
    public string? Name { get; set; }
    public string? Content { get; set; }
    public bool Draft { get; set; } = true;
    public DateTime PublishedAt { get; set; } = DateTime.Now;

    public User User { get; set; }
    public Blog Blog { get; set; }
    public ICollection<Comment>? Comments { get; set; }
    public ICollection<Label>? Labels { get; set; }

    public Post(string slug, string? name, string? content) : base()
    {
        Slug = slug;
        Name = name;
        Content = content;
    }
}

How can I initialize User and Blog with EntityFrameworkCore?

12 Replies

Timo MartinsonOP•16mo ago

This is my DataContext:

public class DataContext : DbContext
{
    public DataContext(DbContextOptions<DataContext> options) : base(options) { }

    public DbSet<User> Users { get; set; }
    public DbSet<Blog> Blogs { get; set; }
    public DbSet<Post> Posts { get; set; }
    public DbSet<Comment> Comments { get; set; }
    public DbSet<Label> Labels { get; set; }
}

public class DataContext : DbContext
{
    public DataContext(DbContextOptions<DataContext> options) : base(options) { }

    public DbSet<User> Users { get; set; }
    public DbSet<Blog> Blogs { get; set; }
    public DbSet<Post> Posts { get; set; }
    public DbSet<Comment> Comments { get; set; }
    public DbSet<Label> Labels { get; set; }
}

blueberriesiftheywerecats•16mo ago

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

Introduction to relationships - EF Core

How to configure relationships between entity types when using Entity Framework Core

blueberriesiftheywerecats•16mo ago

u need to have foreign id inside your models and setup OnModelCreating method

Angius•16mo ago

Either use IDs, or pass a tracked entity

var blog = await _ctx.Blogs.FindAsync(blogId);
var user = await _ctx.Users.FindAsync(userId);

var post = new Post {
    // ...
    Blog = blog,
    User = user,
};

_ctx.Posts.Add(post);
await _ctx.SaveChangesAsync();

var blog = await _ctx.Blogs.FindAsync(blogId);
var user = await _ctx.Users.FindAsync(userId);

var post = new Post {
    // ...
    Blog = blog,
    User = user,
};

_ctx.Posts.Add(post);
await _ctx.SaveChangesAsync();

var post = new Post {
    // ...
    BlogId = blogId,
    UserId = userId,
};

_ctx.Posts.Add(post);
await _ctx.SaveChangesAsync();

var post = new Post {
    // ...
    BlogId = blogId,
    UserId = userId,
};

_ctx.Posts.Add(post);
await _ctx.SaveChangesAsync();

Timo MartinsonOP•16mo ago

how to use IDs in the constructor?!

Angius•16mo ago

Uh, just add them...? Or don't have a constructor

Timo MartinsonOP•16mo ago

ok, thanks! but how to reference _ctx ? where do I get _ctx from?

Angius•16mo ago

It's your database context Inject it

Timo MartinsonOP•16mo ago

could you show me some code?

Angius•16mo ago

[ApiController]
[Route("[controller]")]
public class StuffController
{
    private readonly MyDbContext _ctx;
    public StuffController(MyCbContext ctx)
    {
        _ctx = ctx;
    }

    [HttpGet]
    public async Task<IActionResult>([FromQuery] int id)
    {
        var thing = await _ctx.Things.FindAsync(id);
        return Ok(thing);
    }
}

[ApiController]
[Route("[controller]")]
public class StuffController
{
    private readonly MyDbContext _ctx;
    public StuffController(MyCbContext ctx)
    {
        _ctx = ctx;
    }

    [HttpGet]
    public async Task<IActionResult>([FromQuery] int id)
    {
        var thing = await _ctx.Things.FindAsync(id);
        return Ok(thing);
    }
}

Timo MartinsonOP•16mo ago

nice. thank you!!! 🙂

Accord•16mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

Gaming

Programming

❔ Initializing a relation in Entity Framework Core?