过滤掉Linq中的空值

本文关键字：空值 Linq 过滤 | 更新日期: 2023-09-27 18:17:43

我有以下(工作)代码。这是非常不优雅的，我认为它可以只使用Linq进行重构，从而避免foreach循环，并不得不依赖外部List<>。如何做到这一点?由于

  List<string> answerValues = new List<string>();
  foreach (Fillings filling in fillings)
  {
      string answer = filling.Answers.Where(a => a.Questions == question)
          .Select(a => a.Answer).FirstOrDefault();
      if (!string.IsNullOrEmpty(answer)) answerValues.Add(answer);
  }

过滤掉Linq中的空值

IEnumerable<string> answerValues = fillings
                                    .SelectMany(f => f.Answers)
                                    .Where(a => a.Questions == question)
                                    .Select(a => a.Answer)
                                    .Where(ans => !string.IsNullOrEmpty(ans));

或者如果你需要一个列表:

IList<string> answerValues = fillings
                                    .SelectMany(f => f.Answers)
                                    .Where(a => a.Questions == question)
                                    .Select(a => a.Answer)
                                    .Where(ans => !string.IsNullOrEmpty(ans))
                                    .ToList();

var answerValues = (
    from f in fillings
    from a in f.Answers
    where a.Question == question
    where !String.IsNullOrEmpty(a.Answer)
    select a.Answer).ToList();

fillings.SelectMany(x => x.Answers.Where(a => a.Question == question)
                                  .Select(a => a.Answer)
                                  .FirstOrDefault())
        .Where(x => !string.IsNullOrEmpty(x));
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