使用linq对嵌套列表进行分组

Question

我有一个嵌套的对象列表.我需要分组identifierA和Sum它的数字属性,嵌套列表应分别分组:

public class TypeA
{
    public String identifierA{ get; set; }
    public Int32 number { get; set; }
    public List<TypeB> nestedList { get; set; }
}
public class TypeB
{
    public String identifierB { get; set; }
    public Int32 otherNumber { get; set; }
}

所以我期待这样的事情:

var List<TypeA> groupedList = (from a in TypeAList
                               group a by a.identifierA
                               into groupedData
                               select new TypeA
                               {
                                   identifierA = groupedData.Key,
                                   number = groupedData.Sum(g => g.number ),
                                   nestedList = //HOW TO GROUP NESTED PART?
                               }).ToList();

Answer 1

SelectMany采取IEnumerable<SomethingWithAnIEnumerable>并将所有SomethingWithAnIEnumerable选定的IEnumerables 压缩成一个IEnumerable:

nestedList = groupedData.SelectMany(pa => pa.nestedList).ToList()

Answer 2

我认为这将解决您的问题。

List<TypeA> list = TypeAList
    .GroupBy(a => a.identifierA)
    .Select(
        g =>
        new TypeA
            {
                identifierA = g.Key,
                number = g.Sum(n => n.number),
                nestedList =
                    g.SelectMany(l => l.nestedList)
                    .GroupBy(b => b.identifierB)
                    .Select(
                        gg =>
                        new TypeB
                            {
                                identifierB = gg.Key,
                                otherNumber = gg.Sum(b => b.otherNumber)
                            }).ToList()
            }).ToList();