ASP.NET Core在获取所有数据之前先处理UnitOfWork

Question

I'm implementing a generic repository + Unit of work pattern along with a WebApi project. I'm having problems with getting one entity and including the collection of another enttity that refers to it.

I have the following entities mapped through code first:

public class Ingredient : BaseEntity
{
    public string Name { get; set; }
    public string Amount { get; set; }
    public Guid RecipeId { get; set; }
    public virtual Recipe Recipe { get; set; }
}

public class Recipe : BaseEntity
{
    public string Name { get; set; }
    public string Description { get; set; }
    public string ImagePath { get; set; }
    public virtual ICollection<Ingredient> Ingredients { get; set; }
}

This is my unit of work:

public class UnitOfWork<TContext> : IRepositoryFactory, IUnitOfWork<TContext>, IUnitOfWork where TContext : DbContext
{
    private readonly TContext context;
    private Dictionary<Type, object> repositories;

    public UnitOfWork(TContext context)
    {
        this.context = context ?? throw new ArgumentNullException(nameof(context));
    }

    public TContext Context => context;

    public IRepository<TEntity> GetRepository<TEntity>() where TEntity : BaseEntity
    {
        if (repositories == null)
        {
            repositories = new Dictionary<Type, object>();
        }

        var type = typeof(TEntity);
        if (!repositories.ContainsKey(type))
        {
            repositories.Add(type, new Repository<TEntity>(context));
        }
        return (IRepository<TEntity>)repositories[type];
    }

    public int Commit()
    {
        return context.SaveChanges();
    }

    public void Dispose()
    {
        context?.Dispose();
    }
}

And my generic repository:

public class Repository<T> : IRepository<T> where T : BaseEntity
{
    protected readonly DbContext dbContext;
    protected readonly DbSet<T> dbSet;

    public Repository(DbContext context)
    {
        dbContext = context;
        dbSet = dbContext.Set<T>();
    }

    public T GetEntity(Guid id)
    {
        return dbSet.Find(id);
    }

    public T GetEntity(Guid id, params Expression<Func<T, object>>[] includeProperties)
    {
        IEnumerable<string> properties = GetProperties(includeProperties);

        IQueryable<T> queryable = dbSet;

        foreach (var property in includeProperties)
        {
            queryable = dbSet.Include(property);
        }

        return queryable.FirstOrDefault(x => x.Id == id);
    }

    [...]

    private static IEnumerable<string> GetProperties(Expression<Func<T, object>>[] includeProperties)
    {
        List<string> includelist = new List<string>();

        foreach (var item in includeProperties)
        {
            MemberExpression body = item.Body as MemberExpression;
            if (body == null)
                throw new ArgumentException("The body must be a member expression");

            includelist.Add(body.Member.Name);
        }
        return includelist.AsEnumerable();
    }
}

The controller is injecting the RecipeService. In the controller I have this method:

    [HttpGet("{id}", Name = "Get")]
    public IActionResult Get(Guid id)
    {
        var recipe = recipeService.GetRecipe(id);
        if (recipe == null)
        {
            return NotFound();
        }
        return Ok(recipe);
    }

The recipe service injects the IUnitOfWork and has the following method:

    public Recipe GetRecipe(Guid id)
    {
        return repository.GetEntity(id, r => r.Ingredients);
    }

Also I have the services registered as follows:

        services.AddScoped<IRepositoryFactory, UnitOfWork<TContext>>();
        services.AddScoped<IUnitOfWork, UnitOfWork<TContext>>();
        services.AddScoped<IUnitOfWork<TContext>, UnitOfWork<TContext>>();
        services.AddScoped<IRecipeService, RecipeService>();

My problem is when I'm getting a specified recipe(along with its ingredients) i got a "The connection has been restarted" error (in firefox). While debugging I can see that I have the recipe with its ingredients. But when returning Ok(recipe) and mapping the result to the entities, the IUnitOfWork is disposed after getting the first ingredient.

Anyone can help me out? Thanks

Answer 1

The problem was I was having a circular reference i wasn't getting any exception.

I fixed by adding the following in the ConfigureServices method of the Startup class:

        services.AddMvc().AddJsonOptions(options =>
        {
            options.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
        });