如何在字典列表上动态构建group-by [英] How to build group-by dynamically on a list of dictionaries

问题描述

我试图在IEnumerable上执行一个groupby。问题是编译时我不知道我想要分组的字段。我已经在堆栈上找到了另一篇文章，解释了当类被知道时如何做到这一点并且具有属性，但在我的情况下，我正在处理一个字典，键也只在运行时知道。

我的代码将类似于这样的东西知道这不编译...）：

 私有对象GetValuesGroupedBy（List< string> groupbyNames，List< string> summableNames ）
 {
 //获取网格中的项目列表
 var listOfDicos = grid.AllItems; 
 
 return listOfDicos 
 .GroupBy（x => new {x [groupbyNames [0]]，
x [groupbyNames [1]]，
x [groupbyNames [2 ]]}）
 .Select（group => new {group.Key，
 group.Sum（x => x [summableNames [0]]），
 group.Sum x => x [summableNames [1]]）}）; 
} 
  

任何想法？我已经开始研究动态LINQ，但是被卡住了（因为我没有使用属性，而是使用Key / Value集合）...

感谢大家!!

Sean

解决方案

所以我可以让groupby工作（select语句是另一个问题）。感谢c0d1ng把我放在正确的道路上。语法不是那么简单，因为我使用的是索引器而不是属性...

以下是我的代码：

  private void GetValuesGroupedBy（List< Dictionary< string，object>> list，List< string> groupbyNames，List< string> summableNames）
 {
 //构建groupby字符串
 StringBuilder groupBySB = new StringBuilder（）; 
 groupBySB.Append（new（）; 
 bool useComma = false; 
 foreach（groupbyNames中的var名称）
 {
 if（useComma）
 groupBySB.Append（，）; 
 else 
 useComma = true; 
 
 groupBySB.Append（it [\）; 
 groupBySB。 append（name）; 
 groupBySB.Append（\]）; 
 groupBySB.Append（as）; 
 groupBySB.Append（name）; 
} 
 groupBySB.Append（））; 
 
 var groupby = list.GroupBy（groupBySB.ToString（），it）; 
} 
  

I am trying to perform a groupby on an IEnumerable. The problem is that I do not know at compile-time which fields i want to groupby. I have found another post on stack that explains how to do this when the class is known and has properties, but in my case i am dealing with a dictionary and the keys are also only known at run-time.

My code would resemble something like this (i know this doesn't compile...):

private object GetValuesGroupedBy(List<string> groupbyNames, List<string> summableNames)
{
     // get the list of items in the grid
     var listOfDicos = grid.AllItems;

     return listOfDicos
                .GroupBy(x => new { x[groupbyNames[0]], 
                                    x[groupbyNames[1]], 
                                    x[groupbyNames[2]] })
                .Select(group => new { group.Key, 
                                       group.Sum(x => x[summableNames[0]]), 
                                       group.Sum(x => x[summableNames[1]]) });
}  

Any ideas? I've started looking into Dynamic LINQ but am stuck (because I am not using properties but a Key/Value collection)...

Thanks everybody!!

Sean

解决方案

So I am able to get the groupby to work... (the select statement is another question). Thanks to c0d1ng for putting me on the right path. The syntax was not so trivial because I am using indexers and not properties...

Below is my code:

    private void GetValuesGroupedBy(List<Dictionary<string, object>> list, List<string> groupbyNames, List<string> summableNames)
    {
        // build the groupby string
        StringBuilder groupBySB = new StringBuilder();
        groupBySB.Append("new ( ");
        bool useComma = false;
        foreach (var name in groupbyNames)
        {
            if (useComma)
                groupBySB.Append(", ");
            else
                useComma = true;

            groupBySB.Append("it[\"");
            groupBySB.Append(name);
            groupBySB.Append("\"]");
            groupBySB.Append(" as ");
            groupBySB.Append(name);
        }
        groupBySB.Append(" )");

        var groupby = list.GroupBy(groupBySB.ToString(), "it");
    }

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