c# - 如何在三个集合中进行 LINQ？

Question

我有三个集合:CandidateList、GroupList 和 PositionList。我想找出某个职位是否只有一个候选人，以及该特定组中是否有候选人担任该职位。是这样的:

candidateList = RetrieveCandidates();
groupList = RetrieveGroups();
positionList = RetrievePositions();

//first I loop through the candidates if there is at 
//least 1 candidate per position, INCLUDING THE INDEPENDENT CANDIDATES.


foreach (var pos in positionList)
{
    bool exists = candidateList.Any(x => x.PositionId == pos.PositionId)

    if(!exists)
    {
        //throw exception
    }

}

//then I loop through the groups if there is at least 1 candidate per position. 
//This will make sure that all positions for each group has a member.

foreach (var grp in groupList)
{
    foreach (var pos in positionList)
    {
        bool exists = candidateList.Any(x => x.PositionId == pos.PositionId && x.GroupId == grp.GroupId)

        if(!exists)
        {
            //throw exception
        }
    }
}

有什么方法可以简化代码吗？最好是 LINQ

编辑:我忘了提及独立候选人 (candidate.CandidateId == 0)

Answer 1

您的第一张支票可以减少为:

var exists = positionList.All(p=> candidateList.Any(c=>c.PositionId == p.PositionId));

从那里我们可以创建您的第二张支票

exists = groups.All(
                g =>positionList.All(
                     p=> candidateList.Any(
                          c=>c.PositionId == p.PositionId && c.GroupId == g.GroupId)));