c# - 如何使用单个 linq 查询从点列表中获取 X 和 Y 列表？

Question

我正在生成List<int> x并List<int> y使用List<Point> p此代码：

List<int> x = (from a in p select a.X).ToList();
List<int> y = (from a in p select a.Y).ToList();

那么是否有任何单一的 LINQ 查询来获取x和y来自p？

Answer 1

不，但你可以这样做：

var tuples = p.Select(x => new Tuple<int, int>(x.X, x.Y)).ToList();

但我认为最好的解决方案仍然是这个，使用两个查询：

List<int> x = (from a in p select a.X).ToList();
List<int> y = (from a in p select a.Y).ToList();

Answer 2

你基本上不能，但你可以欺骗自己：

public static class LinqEx
{
    public static void ToLists<T, T1, T2>(this IEnumerable<T> source, SelectorDst<T, T1> selectorDst1, SelectorDst<T, T2> selectorDst2)
    {
        selectorDst1.List.AddRange(source.Select(selectorDst1.Selector));
        selectorDst2.List.AddRange(source.Select(selectorDst2.Selector));
    }
}

public class SelectorDst<T, TList>
{
    public readonly List<TList> List;
    public readonly Func<T, TList> Selector;

    public SelectorDst(List<TList> list, Func<T, TList> selector)
    {
        this.List = list;
        this.Selector = selector;
    }
}

... Some place in the code

var points = new List<Point>();
var xs = new List<int>();
var ys = new List<int>();

points.ToLists(new SelectorDst<Point, int>(xs, p => p.X),
               new SelectorDst<Point, int>(ys, p => p.Y));