使用GroupBy / ToDictionary按List分组 [英] Using GroupBy / ToDictionary grouping by a List

问题描述

Hello C＃gurus和mavens。我有一个问题，我认为其实际上是 .GROUPBY（）问题。



我有一组类型为<的对象b>细胞的。每个单元格都有一个属性 Candidates ，它是一个有序的字符串列表：

Hello C# gurus and mavens. I have a question for you which I believe is actually a .GROUPBY() question.

I have a set of objects of type Cell. Each Cell has a property Candidates which is an ordered list of strings:

public List<string> Candidates { get; private set; }

我想用他们共同的候选人对 Cell 进行分组（例如所有细胞在一组中有候选人{x，y，z}，在另一组中有{x，z}的那些，等等） 。



我的编码类似于以下内容：

I would like to group the Cells by their common Candidates (e.g. all Cells with candidates {"x", "y", "z"} in one group, those with {"x", "z"} into another, etc).

I coded something similar to the following:

cellGroupings = 
  allCells.Where(c => c.Candidates.Count > 0)
          ,GroupBy(c.Candidates)
          .ToDictionary(g => g.Key, g => g);

所以让我们来吧假设allCells有一些单元格集：

So lets assume allCells has some set of cells:

{ Cell.Name = "1st", Cell.Candidates = { "x", "y", "z" } }
{ Cell.Name = "2nd", Cell.Candidates = { "x", "z" }      }
{ Cell.Name = "3rd", Cell.Candidates = { "x", "z" }      }
{ Cell.Name = "4th", Cell.Candidates = { "x", "y", "z" } }

问题在于 GroupBy（）和/或 ToDictionary（）似乎将每个候选列表视为与其他列表不相等，尽管它们具有相同的候选者 。因此，而不是上面生成两个分组（一个用于{x，y，z}一个包含1st和4th，一个用于{x，z}包含2nd 和3rd）它生成四个分组，每个分组1个单元。



是否有一些技巧可以使两个列表看起来相当于 GroupBy（）和/或 ToDictionary（）？

The problem is that GroupBy() and/or ToDictionary() seems to be treating each list of candidates as not-equivalent to the other lists, despite them having the same Candidates. So, instead of the above generating two groupings (one for { "x", "y", "z" } a containing "1st" and "4th", and one for { "x", "z" } containing "2nd" and "3rd") it generates four groupings with 1 Cell each.

Is there some trick to getting two lists to appear equivalent to GroupBy() and/or ToDictionary()?

推荐答案

您好，



它之所以不起作用是因为GroupBy默认使用引用相等比较器，所以即使它们在理论上包含相同的字符串候选，它们实际上并不相等。



我所做的是将每个候选列表转换为这样的直接字符串对象：

Hello,

The reason why it's not working is because GroupBy uses the reference equality comparer by default, so even though they contain the same string candidates in theory, they aren't actually equal.

What I did was convert each of the candidate lists into a direct string object like this:

var cellGroupings = allCells.Where(c => c.Candidates.Any()).GroupBy(c => String.Join(",", c.Candidates.ToArray())).ToDictionary(g=>g.Key, g=>g);

希望它有所帮助！

Hope it helps!

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