在孩子的Linq集合中的最小值为了父集合 [英] Order parent collection by minimum values in child collection in Linq

问题描述

Parent{ List<Child> Children {get;set;} }
Child { int Age {get;set;} }

我想自己的孩子的最低年龄责令家长，着手在平局的情况下，第二或第三个孩子。

I would like to order the parents by the lowest age of their children, proceeding to the second or third child in the case of a tie.

最近我'特地是这样的，它只能由孩子中最小的订单：

The closest I've come is this, which only orders by the youngest child:

parents.OrderBy(p => p.Children.Min(c => c.Age))

这没有考虑第二次（或第三，等在平局的情况下）最年轻的。

This doesn't account for second (or third, etc) youngest in the case of a tie.

由于这些3父母相应的子年龄，我想他们在这才能出来。

Given these 3 parents with corresponding child ages, I'd like them to come out in this order.

• P1 1,2,7


• P2 1,3,6


• P3 1,4,5

推荐答案

所以，你现在要做的，在概念层面，是比较两个序列。而不是试图特殊情况下，它为这个特定序列，我们可以简单的写能力比较任意两个序列的比较器。

So what you're trying to do, at a conceptual level, is compare two sequences. Rather than trying to special case it for this specific sequence, we can simply write a comparer capable of comparing any two sequences.

这将通过序列比较中的项目物品在相同的位置，然后，如果发现一对不相等，它知道结果。

It will go through the items in the sequence compare the items at the same position, and then if it finds a pair that aren't equal, it knows the result.

public class SequenceComparer<TSource> : IComparer<IEnumerable<TSource>>
{
    private IComparer<TSource> comparer;
    public SequenceComparer(IComparer<TSource> comparer = null)
    {
        this.comparer = comparer ?? Comparer<TSource>.Default;
    }
    public int Compare(IEnumerable<TSource> x, IEnumerable<TSource> y)
    {
        return x.Zip(y, (a, b) => comparer.Compare(a, b))
                .Where(n => n != 0)
                .DefaultIfEmpty(x.Count().CompareTo(y.Count()))
                .First();
    }
}

现在打电话时<我们可以简单地使用这个比较器code>排序依据：

var query = parents.OrderBy(parent => parent.Children
    .OrderBy(child => child.Age)
    .Select(child => child.Age)
    , new SequenceComparer<int>());

这篇关于在孩子的Linq集合中的最小值为了父集合的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！