.net 在堆栈溢出时要做到这一点，否则很快就会变成一堆垃圾。回答者的责任不仅仅是看问题的标题。这个“答案”实质上是将一段工作代码从问题转换成方法语法。OP并没有要求这样做，所以答案只不过是无用的杂乱无章的东西，它会跟踪未来的读者。作者应该删除它，但他没有，因为他将

在堆栈溢出时要做到这一点，否则很快就会变成一堆垃圾。回答者的责任不仅仅是看问题的标题。这个“答案”实质上是将一段工作代码从问题转换成方法语法。OP并没有要求这样做，所以答案只不过是无用的杂乱无章的东西，它会跟踪未来的读者。作者应该删除它，但他没有，因为他将失去8点声誉。

foreach (var word in allWords)                                                    
{           
    if (wordCount.ContainsKey(word))
        wordCount[word]++;
    else
        wordCount.Add(word, 1);
}

var wordCountLINQ = (from word in allWordsLINQ
                         group word by word
                         into groups
                         select groups).ToDictionary(g => g.Key, g => g.Count());  

public static void TestCode()
{
    //File can be downloaded from http://norvig.com/big.txt and consists of about a million words.
    const string fileName = @"path_to_file";
    var allWords = from Match m in Regex.Matches(File.ReadAllText(fileName).ToLower(), "[a-z]+", RegexOptions.Compiled)
                   select m.Value;

    var wordCount = new Dictionary<string, int>();
    var timer = new Stopwatch();            
    timer.Start();
    foreach (var word in allWords)                                                    
    {           
        if (wordCount.ContainsKey(word))
            wordCount[word]++;
        else
            wordCount.Add(word, 1);
    }
    timer.Stop();

    Console.WriteLine("foreach loop took {0:0.00} ms ({1:0.00} secs)\n",
            timer.ElapsedMilliseconds, timer.ElapsedMilliseconds / 1000.0);

    //Make LINQ use a different Enumerable (with the exactly the same values), 
    //if you don't it suddenly becomes way faster, which I assmume is a caching thing??
    var allWordsLINQ = from Match m in Regex.Matches(File.ReadAllText(fileName).ToLower(), "[a-z]+", RegexOptions.Compiled)
                   select m.Value;

    timer.Reset();
    timer.Start();
    var wordCountLINQ = (from word in allWordsLINQ
                            group word by word
                            into groups
                            select groups).ToDictionary(g => g.Key, g => g.Count());  
    timer.Stop();

    Console.WriteLine("LINQ took {0:0.00} ms ({1:0.00} secs)\n",
            timer.ElapsedMilliseconds, timer.ElapsedMilliseconds / 1000.0);                     
}

Dictionary<string, int> wordCountLINQ = allWordsLINQ.GroupBy<string, string>(delegate (string word) {
    return word;
}).Select<IGrouping<string, string>, IGrouping<string, string>>(delegate (IGrouping<string, string> groups) {
    return groups;
}).ToDictionary<IGrouping<string, string>, string, int>(delegate (IGrouping<string, string> g) {
    return g.Key;
}, delegate (IGrouping<string, string> g) {
    return g.Count<string>();
});

from word in allWordsLINQ 
group word by word into groups 
select new { Word = groups.Key, Count = groups.Count() }

(from word in allWordsLINQ 
 group word by word into groups 
 select new { Word = groups.Key, Count = groups.Count() })
.ToDictionary(g => g.Word, g => g.Count);

var words = unitOfWork.DepartmentRepository.Get()
           .GroupBy(a=>a.word).Select(s    => new 
           {
             Word = s.Key,
             Count = s.Count()
           }).ToDictionary(d=>d.Word, d=>d.Count);

var wordCountLINQ = allWordsLINQ.Aggregate(new Dictionary<string, int>(), (wcld, w) => { wcld[w] = (wcld.ContainsKey(w) ? wcld[w] : 0) + 1; return wcld; })