通过ThenInclude与EF相关的数据

Question

What is the correct and most performant way to return related data in EF Core?

I'm using a join table UserProjects to represent a many-to-many relationship between users and projects.

(User)1---M(UserProject)M---1(Project)1---M(File)

How would I return all files on a specific project for the current user?

I'm currently doing it like this:

var userId = new Guid(_userManager.GetUserId(User));

var files = _dbContext.Users
                    .Include(up => up.UserProjects)
                    .ThenInclude(p => p.Project)
                    .ThenInclude(f => f.Files)
                    .Where(u => u.Id == userId)
                    .Single()
                    .UserProjects.Select(up => up.Project)
                    .Where(p => p.Id == projectId)
                    .Single().Files.ToList();

Models:

public class ApplicationUser : IdentityUser<Guid>
{
    public virtual ICollection<UserProject> UserProjects { get; set; }
}

public class UserProject
{
    public Guid ApplicationUserId { get; set; }
    public ApplicationUser User { get; set; }

    public Guid ProjectId { get; set; }
    public Project Project { get; set; }
}

public class Project
{
    public Guid Id { get; set; }
    public string Name { get; set; }

    public virtual ICollection<UserProject> UserProjects { get; set; }
    public virtual ICollection<File> Files { get; set; }

}

public class File
{
    public Guid Id { get; set; }
    public string Name { get; set; }

    [Required]
    public Project Project { get; set; }

}

Answer 1

Try this one.

var userId = new Guid(_userManager.GetUserId(User));

var files = _dbContext.Files
               .Include(p => p.Project)
               .ThenInclude(up => up.UserProjects)
               .ThenInclude(u => u.User)
               .Where(x => x.Project.UserProjects.User.Id == userId)
               .ToList();