How should I implement REST API Controller in ASP.NET Core for the resource that has multiple URI endpoints?

Question

Let's say I am modeling blogging REST API which has resources Blog, Post and Comment. Then I add following URIs for Blog and Post resources:

/api/blogs
/api/blogs/{blogId}
/api/blogs/{blogId}/posts

and since deep nesting should be avoided I create separate endpoint for all Posts in order to get their Comment`s:

/api/posts
/api/posts/{postId}
/api/posts/{postId}/comments

Now, since Post resource can be accessed from two different URIs like this:

/api/posts?blogId=123
/api/blogs/123/posts

how should I implement this in ASP.NET Core API project without unnecessary code duplication?

Eg. should I implement both of these endpoints in the same action of the same controller, or should I separate this in two controllers (eg. handle /api/posts?blogId=123 in PostsController and /api/blogs/123/posts in BlogsController)? Also, should I implement POST, PUT and DELETE actions on both endpoints or just choose one as the primary URI?

After I understand how to do this, is it ok to generalize the same approach for other resources with the same kind of relationship (eg. Post and Comment)?

Regarding the database part, there is a nice tutorial that uses Blog and Post: learn.microsoft.com/en-us/ef/core/modeling/… — momo
– momo, Commented Apr 9, 2021 at 8:44
And for the API part, you may find inspiration here: learn.microsoft.com/en-us/aspnet/core/tutorials/… — momo
– momo, Commented Apr 9, 2021 at 8:45

diesel.coder · Accepted Answer · 2021-03-30 14:31:46Z

7

You should make separate controllers for each resource. What those two controllers may share is potentially a PostService or other mechanism for getting posts. Also keep in mind if you are using Entity Framework or some other ORM, the Posts may be exposed on the Blog object through a relationship. Therefore your action might be as simple as:

public async Task<IActionResult> GetPostsForBlog(int blogId)
{
    return Ok(_context.Blogs.Find(blogId).Posts);
}

answered Mar 30, 2021 at 14:31

diesel.coder

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4 Comments

mlst Over a year ago

In which controller should I put this GetPostsForBlog(int blogId) method? Should it go to PostsController or BlogsController (since both of them can return array of posts)?

Feras Salim Over a year ago

surely in post controller

diesel.coder Over a year ago

You should also consider we've only talked about [HttpGet] requests to this point. Consider where the [HttpPost] or [HttpDelete] methods may go. For instance, it would be more likely to me that the [HttpPost] method would be on the posts controller because it would be a little strange (but not impossible) to operate on the Posts collections as part of a call to the Blogs controller like that.

mlst Over a year ago

@diesel.coder could you please provide minimal but complete example code for both controllers so that I can select your answer. Thanks!

iButters · Accepted Answer · 2021-04-02 23:52:53Z

1

I would choose one of both ways and stick with it.

For example, if you are going to pass parameters in the path:

BlogsController

/api/blogs
/api/blogs/{blogId}

PostsController

/api/posts
/api/posts/{postId}
/api/blogs/{blogId}/posts

CommentsController

/api/comments
/api/comments/{commentId}
/api/posts/{postId}/comments

answered Apr 2, 2021 at 23:52

iButters

495 bronze badges

1 Comment

Seeds Over a year ago

The standard is for the CommentsController to have the subroute of /api/comments. You would have to overwrite the convention for this methodology. Not necessarily a bad thing, but I wanted to make a note that this deviates from the standard.

sa-es-ir · Accepted Answer · 2021-04-09 16:45:53Z

0

There is a difference between two approaches and it's about performance issues on database side.

When use /api/blogs/123/posts you need to include Posts in Blog object like this:

 _dbContext.Blogs
 .AsNoTracking()
 .Include(x => x.Posts)
 .Where(x => x.Id == 123)
 .FirstOrDefaultAsync();

And this will be translated to T-Sql and use Inner Join or Left Join (based on required relations) between blog table and post table some thing like this:

Select * from (Select top 1 * from dbo.Blogs where Id = 123) b 
Left Join dbo.Posts p on b.Id = p.BlogId

But when call /api/posts?blogId=123 you can simply query on Post object like this:

_dbContext.Posts
.AsNoTracking()
.Where(x => x.BlogId == 123)
.ToListAsync();

And this will be translated to T-Sql like this:

Select * from dbo.Posts where BlogId=123

As you may be guessed the second query is faster than first.

If you want to follow Rest Api standard you should follow the first one but for get better performance use second query for get Posts items and no need implement two approaches, just pick one because with implement two approaches already you implement logic in two places and if logic changed you should change two place of your code.

edited Apr 9, 2021 at 16:45

answered Apr 9, 2021 at 9:10

sa-es-ir

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2 Comments

momo Over a year ago

Sidenote: FirstOrDefaultAsync() results in SELECT TOP(1) ...

sa-es-ir Over a year ago

@momo yes you right. But I just show what happens in database and I know that sql select top one from blog table and get related posts with join. Thanks for your point.

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