C#•10mo ago

Minimal API : Model / DTO Help

Hello! I'm new here and I'm looking for some help on my project. 🙂 I'm working on building a website for my portfolio. I've got a Blazor frontend, and I'm using a minimal API for my backend. I have models for BlogPosts, Projects and Tags. I am also using DTOs for each. I decided to use DTOs to prevent cyclical relationships but I keep running into them. I'm quite new to this side of .NET and using Databases. I've been at this for a while and having a hard time getting it to work how I'd like it to. From my BlogEndpoints, I'd like my GET requests to get all my blogs from the database, which is what it does currently, but it shows me only the IDs of the Tags and Projects. I think showing just the ID for the Project is fine since I'll be able to use the id in a link using said ID. I'd like to have a List<Tag> Tags in each of my BlogPost so that I can just iterate through and do something like this on my Blazor end :

foreach(Tag tag in blogPost.Tags){
  <TagItem Data=tag/>
}

foreach(Tag tag in blogPost.Tags){
  <TagItem Data=tag/>
}

I'm sure there are better ways, but that's why I came here to ask for some advice. If I can figure out how to fix this on my Blog endpoint, I'll be able to fix it on my Project endpoint as well. Here are the Model and DTO for my BlogPost, as well as my GET and POST request for my endpoint

namespace BackEndAPI.DTOs
{
    public class BlogPostDTO {
        [Required]
        public string Title { get; set; }
        [Required]
        public string Body { get; set; }
        [Required]
        public string Summary { get; set; }
        public int? ProjectId { get; set; }
        public List<int> TagIds { get; set; } = new List<int>();
    }
}

namespace BackEndAPI.DTOs
{
    public class BlogPostDTO {
        [Required]
        public string Title { get; set; }
        [Required]
        public string Body { get; set; }
        [Required]
        public string Summary { get; set; }
        public int? ProjectId { get; set; }
        public List<int> TagIds { get; set; } = new List<int>();
    }
}

namespace BackEndAPI.Models
{
    public class BlogPost {
        public int Id { get; set; }
        [Required]
        public string Title { get; set; }
        [Required]
        public string Body { get; set; }
        [Required]
        public string Summary { get; set; }
        [Required]
        public DateTime CreatedOn { get; set; } = DateTime.UtcNow;

        public int? ProjectId { get; set; }
        [JsonIgnore]
        public Project? Project { get; set; }
        [JsonIgnore]
        public List<Tag> Tags { get; set; } = new();
    }
}

namespace BackEndAPI.Models
{
    public class BlogPost {
        public int Id { get; set; }
        [Required]
        public string Title { get; set; }
        [Required]
        public string Body { get; set; }
        [Required]
        public string Summary { get; set; }
        [Required]
        public DateTime CreatedOn { get; set; } = DateTime.UtcNow;

        public int? ProjectId { get; set; }
        [JsonIgnore]
        public Project? Project { get; set; }
        [JsonIgnore]
        public List<Tag> Tags { get; set; } = new();
    }
}

private static async Task<IResult> GetBlogs(ApplicationDbContext db)
        {
            var blogPosts = await db.Blogs.Include(b => b.Tags).ToListAsync();
            return Results.Ok(blogPosts);
        }

        private static async Task<IResult> GetBlogById(int id, ApplicationDbContext db)
        {
            var blogPost = await db.Blogs.SingleOrDefaultAsync(b => b.Id == id);
            return Results.Ok(blogPost);
        }

        private static async Task<IResult> CreateBlog(BlogPostDTO dto, ApplicationDbContext db)
        {
            var tags = await db.Tags.Where(t => dto.TagIds.Contains(t.Id)).ToListAsync();
            var project = await db.Projects.Where(p => dto.ProjectId == p.Id).ToListAsync();
            var blogPost = new BlogPost
            {
                Title = dto.Title,
                Body = dto.Body,
                Summary = dto.Summary,
                ProjectId = dto.ProjectId,
                Project = project[0],
                Tags = tags,
            };

            db.Blogs.Add(blogPost);
            await db.SaveChangesAsync();
            return Results.Created($"/blogs/{blogPost.Id}", blogPost);
        }

private static async Task<IResult> GetBlogs(ApplicationDbContext db)
        {
            var blogPosts = await db.Blogs.Include(b => b.Tags).ToListAsync();
            return Results.Ok(blogPosts);
        }

        private static async Task<IResult> GetBlogById(int id, ApplicationDbContext db)
        {
            var blogPost = await db.Blogs.SingleOrDefaultAsync(b => b.Id == id);
            return Results.Ok(blogPost);
        }

        private static async Task<IResult> CreateBlog(BlogPostDTO dto, ApplicationDbContext db)
        {
            var tags = await db.Tags.Where(t => dto.TagIds.Contains(t.Id)).ToListAsync();
            var project = await db.Projects.Where(p => dto.ProjectId == p.Id).ToListAsync();
            var blogPost = new BlogPost
            {
                Title = dto.Title,
                Body = dto.Body,
                Summary = dto.Summary,
                ProjectId = dto.ProjectId,
                Project = project[0],
                Tags = tags,
            };

            db.Blogs.Add(blogPost);
            await db.SaveChangesAsync();
            return Results.Created($"/blogs/{blogPost.Id}", blogPost);
        }

Maybe DTOs aren't needed. Maybe I should do away with the List<Tag> Tags in my model and just use a List<int> TagIds instead and then ask the database what each Id corresponds to. I'm not sure which direction I should head. Any and all feedback and help would be greatly appreciated 🙂

20 Replies

Angius•10mo ago

Why do yout database models have [JsonIgnore] if you're using DTOs?

TrustyTeaOP•10mo ago

I was running into cycles and thought that might help. It might have been left over from a few things I was trying and forgot to remove it after I changed up the Model & DTO.

Angius•10mo ago

You should be returning a DTO from your endpoints As it stands, none of them do that

Pobiega•10mo ago

the only DTO I see is the incomming DTO in CreateBlog, which isnt usually what we mean when we say "DTO" in C# land

Angius•10mo ago

var project = await db.Projects.Where(p => dto.ProjectId == p.Id).ToListAsync();

var project = await db.Projects.Where(p => dto.ProjectId == p.Id).ToListAsync();

also, you can use .FirstOrDefaultAsync() instead, to avoid the Project = project[0],

Pobiega•10mo ago

thats just a normal request object

TrustyTeaOP•10mo ago

Ahh okay, maybe I'll spend a little more time to learn about DTO's then. I thought they were for incoming objects and not for outgoing but it does make sense. Thanks for the tip on the .FirstOrDefaultAsync() too!

Pobiega•10mo ago

its actually mostly for outgoing we use them

Angius•10mo ago

To avoid cycles you want to .Select() into a DTO, that allows you to omit the properties that would cause a cycle issue

TrustyTeaOP•10mo ago

So I'd be creating a new DTO in the requests, and populating it with the data from the database? I had something like this before I went to what I have now:

private static async Task<IResult> GetBlogs(ApplicationDbContext db) {
            var blogDtos = await db.Blogs
                .Include(b => b.Tags)
                .Select(b => new BlogDTO
                {
                    Id = b.Id,
                    Title = b.Title,
                    Summary = b.Summary,
                    Body = b.Body,
                    CreatedOn = b.CreatedOn,
                    Tags = b.Tags.Select(t => new TagDTO { Id = t.Id, Name = t.Name }).ToList(),
                    AssociatedProjectId = b.AssociatedProjectId
                })
                .ToListAsync();
            return Results.Ok(blogDtos);
        }

private static async Task<IResult> GetBlogs(ApplicationDbContext db) {
            var blogDtos = await db.Blogs
                .Include(b => b.Tags)
                .Select(b => new BlogDTO
                {
                    Id = b.Id,
                    Title = b.Title,
                    Summary = b.Summary,
                    Body = b.Body,
                    CreatedOn = b.CreatedOn,
                    Tags = b.Tags.Select(t => new TagDTO { Id = t.Id, Name = t.Name }).ToList(),
                    AssociatedProjectId = b.AssociatedProjectId
                })
                .ToListAsync();
            return Results.Ok(blogDtos);
        }

I'll have to go back to this and figure it out now that I know to use DTOs as outgoing too. IIRC I wasn't getting the Tags in the response, just the IDs

Pobiega•10mo ago

yep that looks about right at a glance

Angius•10mo ago

But you're getting blogs... twice For some reason

Pobiega•10mo ago

oh yep :p change it to just return the blogDtos

TrustyTeaOP•10mo ago

Ah oops that's a copy error :P, that's not actually there sorry

Angius•10mo ago

private static async Task<IResult> GetBlogs(ApplicationDbContext db) {
            var blogDtos = await db.Blogs
-               .Include(b => b.Tags)
                .Select(b => new BlogDTO
                {
                    Id = b.Id,
                    Title = b.Title,
                    Summary = b.Summary,
                    Body = b.Body,
                    CreatedOn = b.CreatedOn,
                    Tags = b.Tags.Select(t => new TagDTO { Id = t.Id, Name = t.Name }).ToList(),
                    AssociatedProjectId = b.AssociatedProjectId
                })
                .ToListAsync();
-           var blogPosts = await db.Blogs.ToListAsync();
-           return Results.Ok(blogPosts);
+           return Results.Ok(blogDtos);

        }

private static async Task<IResult> GetBlogs(ApplicationDbContext db) {
            var blogDtos = await db.Blogs
-               .Include(b => b.Tags)
                .Select(b => new BlogDTO
                {
                    Id = b.Id,
                    Title = b.Title,
                    Summary = b.Summary,
                    Body = b.Body,
                    CreatedOn = b.CreatedOn,
                    Tags = b.Tags.Select(t => new TagDTO { Id = t.Id, Name = t.Name }).ToList(),
                    AssociatedProjectId = b.AssociatedProjectId
                })
                .ToListAsync();
-           var blogPosts = await db.Blogs.ToListAsync();
-           return Results.Ok(blogPosts);
+           return Results.Ok(blogDtos);

        }

And no need for an include with a select

TrustyTeaOP•10mo ago

Oh ok, is it because I have this line? Tags = b.Tags.Select(t => new TagDTO { Id = t.Id, Name = t.Name }).ToList(), Or the .Select() right below the .Include()?

Angius•10mo ago

In general But I guess more so because of the select into blogpost DTO You explicitly select some parts of the tags, so there's no need to include all of them in their entirety

TrustyTeaOP•10mo ago

I see 🤔 , yeah that makes sense. I also need to practice and learn some more LINQ. Thanks for the help! Just knowing that I should be using DTOs as part of my responses is enough of a direction to get me started on it. If I have some more questions, am I ok to come back to this thread?

Pobiega•10mo ago

sure

TrustyTeaOP•10mo ago

Sweet thank you! 😄

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Minimal API : Model / DTO Help