hn-dotnet/Application/GetLink/GetLinkQueryHandler.cs

using System.Threading;
using System.Linq;
using System.Threading.Tasks;
using MediatR;
using HN.Domain;

namespace HN.Application
{
  public sealed class GetLinkQueryHandler : IRequestHandler<GetLinkQuery, LinkDto>
  {
    private readonly IHNContext _context;

    public GetLinkQueryHandler(IHNContext context)
    {
      _context = context;
    }

    public Task<LinkDto> Handle(GetLinkQuery request, CancellationToken cancellationToken)
    {
      var result = from link in _context.Links
                   join user in _context.Users on link.CreatedBy equals user.Id
                   where link.Id == request.Id
                   select new LinkDto
                   {
                     Id = link.Id,
                     Url = link.Url,
                     CreatedByName = user.UserName,
                     CreatedAt = link.CreatedAt,
                     UpVotes = link.Votes.Count(v => v.Type == VoteType.Up),
                     DownVotes = link.Votes.Count(v => v.Type == VoteType.Down)
                   };

      return Task.FromResult(result.SingleOrDefault());
    }
  }
}