ToLookup有多个键

问题描述

有没有一种方法，要求多个密钥由LINQ提供的 .ToLookup 功能？我承认，这似乎不直观起初，我很期待，有没有实际的方式来做到这一点，但我希望有人知道的方式。

基本上，我希望能够通过两个值来查找，例如字符串和 INT ，和检索与这两个值的对象。

示例

 公共类MyClass的{
      公共字符串StringProp {获取;集;}
      公众诠释IntProp {获取;集;}
      公共对象MOREDATA {获取;集;}
    }
    公共类主要{
      公共无效的主要（）{
        HashSet的＆LT; MyClass的＆GT;设置=新的HashSet＆LT; MyClass的＆GT;（）;
        set.Add（新MyClass的{StringProp =一个，IntProp = 1，MOREDATA =空}）;
        set.Add（新MyClass的{StringProp =c的，IntProp = 4，MOREDATA =新对象（）}）;
        set.Add（新MyClass的{StringProp =一个，IntProp = 2，MOREDATA =upupdowndown}）;
        set.Add（新MyClass的{StringProp =C，IntProp = 1，= MOREDATA的String.Empty}）;
        set.Add（新MyClass的{StringProp =C，IntProp = 4，MOREDATA =的String.Empty}）;
        //使用'变种'，因为我不知道如何做到这一点定义。
        //我认识到，这将不会编译 - 而这就是我想要做的。
        VAR查找= set.ToLookup（X =＆GT; x.StringProp和放大器;＆安培; x.IntProp）
        MyClass的C =查找[一个，1]。首先（）; //如果返回的第一个元素
        IEnumerable的＆LT; MyClass的＆GT;名单=查找[C，4]。 //应该返回第二个和最后一个元素
      }
    }
 

解决方案

我会使用元组 S表示这样的事情：

  VAR查找= set.ToLookup（X =＆GT; Tuple.Create（x.StringProp，x.IntProp））;
。MyClass的C =查找[Tuple.Create（一，1）]首先（）;
IEnumerable的＆LT; MyClass的＆GT;名单=查找[Tuple.Create（C，4）];
 

Is there a way to require multiple keys for the .ToLookup function provided by LINQ? I will admit that this seems non-intuitive at first, and I'm expecting that there's no actual way to do this but I'm hoping that someone knows a way.

I basically want to be able to lookup by two values, for example a string and an int, and retrieve the object with those two values.

Example

    public class MyClass {
      public string StringProp {get;set;}
      public int IntProp {get;set;}
      public object MoreData {get;set;}
    }
    public class Main {
      public void Main() {
        HashSet<MyClass> set = new HashSet<MyClass>();
        set.Add(new MyClass {StringProp = "a", IntProp = 1, MoreData = null});
        set.Add(new MyClass {StringProp = "c", IntProp = 4, MoreData = new object()});
        set.Add(new MyClass {StringProp = "a", IntProp = 2, MoreData = "upupdowndown"});
        set.Add(new MyClass {StringProp = "c", IntProp = 1, MoreData = string.Empty});
        set.Add(new MyClass {StringProp = "c", IntProp = 4, MoreData = string.Empty});
        // Using 'var' because I don't know how this would be defined.
        // I recognize that this will not compile - but this is what I'm trying to do.
        var lookup = set.ToLookup(x => x.StringProp && x.IntProp)
        MyClass c = lookup["a", 1].First(); // Should return the first element
        IEnumerable<MyClass> list = lookup["c", 4]; // Should return the 2nd and last elements
      }
    }

解决方案

I would use Tuples for this sort of thing:

var lookup = set.ToLookup(x => Tuple.Create(x.StringProp, x.IntProp));
MyClass c = lookup[Tuple.Create("a", 1)].First();
IEnumerable<MyClass> list = lookup[Tuple.Create("c", 4)];

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