Question

我有一个答案实体列表（列表大小为50-2000个项目 - 实体具有比此处所示更多的属性）我想要一个linq查询来为那些尚未得到正确答案的人选择所有实体所以我的实体输出列表将通过fred和harry从下表中排除所有实体，因为它们每个都有正确的答案 - 并且包括所有带有bob和bill的答案的实体 - 我必须在isCorrect上选择而不是在答案本身上当呈现给用户时，答案被扰乱，我也需要完整的实体。

- username | answer | isCorrect | .....
- fred     |  a     | false            exclude as he has 1 correct
- fred     |  d     | false            exclude as he has 1 correct
- fred     |  b     | false            exclude as he has 1 correct     
- fred     |  a     | true             exclude as he has 1 correct
+ bob      |  a     | false          need this entity
+ bob      |  b     | false          need this entity
+ bill     |  a     | false          need this entity    
+ bill     |  b     | false          need this entity   
- harry    |  a     | false            exclude as he has 1 correct   
- harry    |  b     | true             exclude as he has 1 correct     
- harry    |  c     | false            exclude as he has 1 correct

我可以获得没有正确答案的用户列表

var usersWithNoCorrectAnswers = entities
  .GroupBy(a => a.UserName)
  .Where(g => g.Any(x => !x.IsCorrect))
  .Select(g => g.Key)
  .ToList();

但我不确定如何获得没有正确答案的实体列表感谢

Answer 1

要让获得所有答案错误的用户获得所有实体，您可以对用户名进行分组并筛选出任何正确的用户。然后只需选择组的实体并展平结果。

var results = entities.GroupBy(a => a.UserName(
    .Where(g => !g.Any(a => a.IsCorrect))
    .SelectMany(g => g)
    .ToList();

Answer 2

我认为你需要这样的东西：

var results = entities.GroupBy(a => a.UserName(
    .Where(g => !g.Any(a => a.IsCorrect))
    .SelectMany(g => g.Select(a => 
          new {
               username = a.username,
               answer = a.answer,
               ...
          }
     ))
    .Distinct()
    .ToList();

或者

var results = entities.GroupBy(a => a.UserName(
    .Where(g => !g.Any(a => a.IsCorrect))
    .SelectMany(g => g.Select(a => a))
    .Distinct()
    .ToList();

Answer 3

但我不确定如何获得没有正确答案的实体列表

var noCorrectAnswers = entities
    .GroupBy(q => q.UserName)
    .Where(g => !g.Any(a => a.IsCorrect))
    .SelectMany(g => g)
    .ToList();

C＃linq选择一些实体

3 个答案: