建设项目数的词典列表中 [英] Building a dictionary of counts of items in a list

问题描述

我有一个包含一串字符串，可以出现多次的List。我想借这个名单，并建立列表项为重点和它们的出现为价值的计数的字典

例如：

 列表<串GT;东西=新的List<串GT;（）; 
 stuff.Add（花生酱）; 
 stuff.Add（大灌篮）; 
 stuff.Add（食品）; 
 stuff.Add（小吃）; 
 stuff.Add（哲学）; 
 stuff.Add（花生酱）; 
 stuff.Add（大灌篮）; 
 stuff.Add（食品）; 
  

和结果将是包含字典：

 花生酱，2 
大灌篮，2 
民以食为天，2 
小吃，1 
哲学，1 
  

我有办法做到这一点，但它似乎并不像我利用好东西用C＃m的3.0

 公众解释<字符串，整数> CountStuff（IList的<串GT; stuffList）
 {
&字典LT;字符串，整数> stuffCount =新词典<字符串，整数>（）; 
 
的foreach（在stuffList串的东西）{
 //初始化或增加计数此项目
如果（stuffCount.ContainsKey（东西））{
 stuffCount [东东] ++; 
}其他{
 stuffCount.Add（东东，1）; 
} 
} 
 
返回stuffCount; 
} 
  

解决方案

您可以使用group子句。在C＃中做到这一点。

 列表<串GT;东西=新的List<串GT;（）; 
 ... 
 
组VAR =从s的东西组由s s转换g选择
 {新东西= g.Key，计数= g.Count（）}; 
  

您可以调用扩展方法直接，以及如果你想：

  VAR组= stuff.GroupBy（S = GT S）。选择（
S =>新建{东西= s.Key，计数= S .Count之间的（）}）; 
  

从这里它是一个短的一跳将其放入一个词典<字符串， INT> ：

  VAR词典= groups.ToDictionary（G => g.Stuff，G = GT; g.Count）; 
  

I have a List containing a bunch of strings that can occur more than once. I would like to take this list and build a dictionary of the list items as the key and the count of their occurrences as the value.

Example:

List<string> stuff = new List<string>();
stuff.Add( "Peanut Butter" );
stuff.Add( "Jam" );
stuff.Add( "Food" );
stuff.Add( "Snacks" );
stuff.Add( "Philosophy" );
stuff.Add( "Peanut Butter" );
stuff.Add( "Jam" );
stuff.Add( "Food" );

and the result would be a Dictionary containing:

"Peanut Butter", 2
"Jam", 2
"Food", 2
"Snacks", 1
"Philosophy", 1

I have a way to do this, but it doesn't seem like I'm utilizing the good stuff in C# 3.0

public Dictionary<string, int> CountStuff( IList<string> stuffList )
{
    Dictionary<string, int> stuffCount = new Dictionary<string, int>();

    foreach (string stuff in stuffList) {
    	//initialize or increment the count for this item
    	if (stuffCount.ContainsKey( stuff )) {
    		stuffCount[stuff]++;
    	} else {
    		stuffCount.Add( stuff, 1 );
    	}
    }

    return stuffCount;
}

解决方案

You can use the group clause in C# to do this.

List<string> stuff = new List<string>();
...

var groups = from s in stuff group s by s into g select 
    new { Stuff = g.Key, Count = g.Count() };

You can call the extension methods directly as well if you want:

var groups = stuff.GroupBy(s => s).Select(
    s => new { Stuff = s.Key, Count = s.Count() });

From here it's a short hop to place it into a Dictionary<string, int>:

var dictionary = groups.ToDictionary(g => g.Stuff, g => g.Count);

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