當我執行 linq 時，我得到了空集合，其中通過比較 Guid

Question

public ServiceResponce Write(Guid senderID, Guid reciverID, string body)
    {
        Message message = new Message
        {
            Body = body
        };

        var reciver = context.Users.Where(c => c.Id == reciverID).Single();
        var sender = context.Users.Where(c => c.Id == senderID).Single();

        message.Sender = sender;
        message.Reciver = reciver;
        context.SaveChanges();

        return new ServiceResponce();
    }

我得到了空序列的例外。 我從HTTPContext.Users.FindFirstValue(ClaimTypes.NameIdentifier)獲得 Guid id 結果，我得到的結果不是 null。 我無法解決這個問題。
調用方法：

 public IActionResult Wright(Guid reciverID,string body)
    {
        var userID = HttpContext.User.FindFirstValue(ClaimTypes.NameIdentifier);
        var neededID = Guid.Parse(userID);
        _chatService.Write(neededID, reciverID, body);
        return Ok();
    }

Answer 1

嘗試這個：

public ServiceResponce Write(...)
{
    ...
    var reciver = context.Users.Where(c => c.Id == reciverID).SingleOrDefault();
    var sender = context.Users.Where(c => c.Id == senderID).SingleOrDefault();

    if(reciver == null || sender ==null)
    {
       //Log??
       return null;
    }
    ...
    
}


public IActionResult Wright(Guid reciverID,string body)
{
    var userID = HttpContext.User.FindFirstValue(ClaimTypes.NameIdentifier);

    // If you really want to put the validation logic here
    Guid neededID;   
    if (!Guid.TryParse(userId, out var neededID))
    {
       //Log?
       return BadRequest();
    }

    if(_chatService.Write(neededID, reciverID, body) == null)
       return BadRequest();
    return Ok();
}