ASP.NET 核心 Web API 关系数据 - 错误 504

Question

I've been trying to develop my first Web API project in .NET Core. I'm currently experiencing an issue when I retrieve relational data. I'm using the repository model.

At the moment, I have the following in my repository class:

    public IEnumerable<Children> GetAll()
    {
        return _context.Children;
    }

    public IEnumerable<Children> GetAll(int parentId)
    {
        return _context.Children.Where(c => c.ParentId == parentId).Include(c=>c.Parent);
    }

When I try calling the GetAll() function in Fiddler, it works fine. But when I try the GetAll(int parentId) function, I get a 504 Error.

I've set breakpoints in visual studio to test the data being returned by the second method and it returns the data okay.

The Controller method that calls this function is:

    [Route("[action]")]
    [HttpGet]
    [Produces(typeof(DbSet<Children>))]
    public IActionResult GetChildrenOfCurrentLoggedInUser()
    {
        if (LoggedInUser.Id == null)
        {
            return null;
        }

        if (LoggedInUser.ParentId == 0)
        {
            var parent = _parentRepository.Find(LoggedInUser.Id);
            LoggedInUser.ParentId = parent.Result.Id;
        }

        var results = new ObjectResult(_childRepository.GetAll(LoggedInUser.ParentId))
        {
            StatusCode = (int)HttpStatusCode.OK
        };

        Request.HttpContext.Response.Headers.Add("X-Total-Count", _childRepository.GetAll(LoggedInUser.ParentId).Count().ToString());

        return results;
    }

It all seems to check out until it gives me the error.

Edit:

I've done some digging and realised I'm getting similar issues with the POST as well. The code within the POST works perfectly but the response is giving me errors.

The following code works in that it saves the data correctly but it doesn't provide a valid response.

    [HttpPost]
    [Produces(typeof(Children))]
    public async Task<IActionResult> PostChildren([FromBody]ChildMinimalDTO child)
    {
        if (LoggedInUser.Id == null)
        {
            return BadRequest(ModelState);
        }

        if (!ModelState.IsValid)
        {
            return BadRequest(ModelState);
        }

        var parent = _parentRepository.Find(LoggedInUser.Id);

        // Get the parentID from the current logged in user
        if (LoggedInUser.ParentId == 0)
        {
            LoggedInUser.ParentId = parent.Result.Id;
        }

        DateTime dateOfBirth = new DateTime(child.YearOfBirth, child.MonthOfBirth, child.DayOfBirth);
        Children newChild = new Children()
        {
            ChildName = child.ChildName,
            Dob = dateOfBirth,
            IsMale = child.IsMale,
            ParentId = LoggedInUser.ParentId,
        };

        await _childRepository.Add(newChild);

        return CreatedAtAction("PostChildren", new { id = newChild.Id }, newChild);
    }

But, if I make a minor change, it provides a valid response.

    [HttpPost]
    [Produces(typeof(Children))]
    public async Task<IActionResult> PostChildren([FromBody]ChildMinimalDTO child)
    {
        if (LoggedInUser.Id == null)
        {
            return BadRequest(ModelState);
        }

        if (!ModelState.IsValid)
        {
            return BadRequest(ModelState);
        }

        var parent = _parentRepository.Find(LoggedInUser.Id);

        // Get the parentID from the current logged in user
        if (LoggedInUser.ParentId == 0)
        {
            LoggedInUser.ParentId = parent.Result.Id;
        }

        DateTime dateOfBirth = new DateTime(child.YearOfBirth, child.MonthOfBirth, child.DayOfBirth);
        Children newChild = new Children()
        {
            ChildName = child.ChildName,
            Dob = dateOfBirth,
            IsMale = child.IsMale,
            ParentId = LoggedInUser.ParentId,
        };

        await _childRepository.Add(newChild);

        newChild.Parent = null;

        return CreatedAtAction("PostChildren", new { id = newChild.Id }, newChild);
    }

The only change was to mane newChild.Parent null. There does seem to be a problem with it responding correctly when the relational data is added to the response. With the earlier issue, if I remove the.include from the second function, it works.

These are the models I'm working with:

public class ChildMinimalDTO
{
    public string ChildName;
    public int DayOfBirth;
    public int MonthOfBirth;
    public int YearOfBirth;
    public bool IsMale;
    public int ParentId;
}

public partial class Children
{
    public Children()
    {
        Diaries = new HashSet<Diaries>();
    }

    public long Id { get; set; }
    public string ChildName { get; set; }
    public DateTime Dob { get; set; }
    public bool IsMale { get; set; }
    public int ParentId { get; set; }

    public Parents Parent { get; set; }
    public ICollection<Diaries> Diaries { get; set; }
}

public partial class Parents
{
    public Parents()
    {
        Children = new HashSet<Children>();
        SecurityQuestionParents = new HashSet<SecurityQuestionParents>();
    }

    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Address { get; set; }
    public string Address2 { get; set; }
    public string Town { get; set; }
    public string PostCode { get; set; }
    public int CountryId { get; set; }
    public string AspNetUserId { get; set; }

    public Countries Country { get; set; }
    public ICollection<Children> Children { get; set; }
    public ICollection<SecurityQuestionParents> SecurityQuestionParents { get; set; }
}

And this is what I have in my startup class:

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddScoped<ICountryRepository, CountryRepository>();
        services.AddScoped<IParentRepository, ParentRepository>();
        services.AddScoped<IChildRepository, ChildRepository>();
        services.AddScoped<IDiaryEntryRepository, DiaryEntryRepository>();
        services.AddScoped<IDiaryRepository, DiaryRepository>();
        services.AddScoped<IImageRepository, ImageRepository>();

        services.Configure<CookiePolicyOptions>(options =>
        {
            // This lambda determines whether user consent for non-essential cookies is needed for a given request.
            options.CheckConsentNeeded = context => true;
            options.MinimumSameSitePolicy = SameSiteMode.None;
        });

        services.AddDbContext<ApplicationDbContext>(options =>
            options.UseSqlServer(
                Configuration.GetConnectionString("DefaultConnection")));

        services.AddIdentity<ApplicationUser, IdentityRole>()
            .AddDefaultUI()
            .AddDefaultTokenProviders()
            .AddEntityFrameworkStores<ApplicationDbContext>();

        services.AddDbContext<ApplicationDbContext>(options => options.UseSqlServer("Data Source=184.168.194.60;Initial Catalog=Child_One;User ID=TickledPink;Password=ans10tech!;"));

        services.AddMvc().AddJsonOptions(options =>
        {
            options.SerializerSettings.ContractResolver = new Newtonsoft.Json.Serialization.DefaultContractResolver();
        });

        services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1)
            .AddRazorPagesOptions(options =>
            {
                options.AllowAreas = true;
                options.Conventions.AuthorizeAreaFolder("Identity", "/Account/Manage");
                options.Conventions.AuthorizeAreaPage("Identity", "/Account/Logout");
            });

        services.ConfigureApplicationCookie(options =>
        {
            options.LoginPath = $"/Identity/Account/Login";
            options.LogoutPath = $"/Identity/Account/Logout";
            options.AccessDeniedPath = $"/Identity/Account/AccessDenied";
        });

        services.AddHttpContextAccessor();
        services.AddSingleton<IActionContextAccessor, ActionContextAccessor>();
        services.AddSingleton<IEmailSender, EmailSender>();

        services.AddTransient<IPrincipal>(provider => provider.GetService<IHttpContextAccessor>().HttpContext.User);
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IHostingEnvironment env, IServiceProvider serviceProvider)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
            app.UseDatabaseErrorPage();
        }
        else
        {
            app.UseExceptionHandler("/Home/Error");
            app.UseHsts();
        }

        app.UseHttpsRedirection();
        app.UseStaticFiles();
        app.UseCookiePolicy();

        app.UseAuthentication();

        app.UseMvc(routes =>
        {
            routes.MapRoute(
                name: "default",
                template: "{controller=Home}/{action=Index}/{id?}");
        });

        // For Unity WebGL integration
        app.UseFileServer();
        StaticFileOptions staticFileOptions = new StaticFileOptions()
        {
            FileProvider = new PhysicalFileProvider(
                Path.Combine(Directory.GetCurrentDirectory(), @"Template")),
            RequestPath = new PathString("/template")
        };
        app.UseStaticFiles(staticFileOptions);
        FileExtensionContentTypeProvider contentTypeProvider = (FileExtensionContentTypeProvider)staticFileOptions.ContentTypeProvider ??
            new FileExtensionContentTypeProvider();
        contentTypeProvider.Mappings.Add(".unityweb", "application/octet-stream");
        staticFileOptions.ContentTypeProvider = contentTypeProvider;
        app.UseStaticFiles(staticFileOptions);

        //CreateRoles(serviceProvider);
    }

Answer 1

Solved it. The error appeared to be down to the fact that it was retrieving cyclic results because of the link between the Parent and Children models.

This post gave me the answer.

Asp.Net Core Web API 2.2 Controller not returning complete JSON