用lambdas替换嵌套的foreach c＃

Question

是否可以使用lambdas而不是foreachs来表达以下代码块？

    IEnumerable<BODSurveys.SurveysAnwer> resp = new List<SurveysAnwer>();
    foreach (var section in Sections)
    {
      foreach (var question in section.Questions)
      {
        foreach (var answer in question.SurveysAnwers)
        {
          yield return answer;
        }
      }
    }

Answer 1

是：

return Sections.SelectMany(s => s.Questions.SelectMany(q => q.SurveyAnswers));