将IQueryable<object>结果转换为逗号分隔的字符串

你可以使用它 String.Join 创建逗号分隔的字符串。

string DetailsOfSickness = 
    String.Join(", ", (
      from t2 in illnesses
      join ai1 in absenceIllnesses on t2.IllnessID equals ai1.IllnessID
      select t2.IllnessName).ToArray());

像这样的东西应该可以做到:

DetailsOfSickness = String.Join(", ", (
  from t2 in Illnesses
  join ai1 in AbsenceIllnesses on t2.IllnessID equals ai1.IllnessID
  select t2.IllnessName).ToArray());