查询字典以获取前 3 个最常见的元素

Question

所以我有一个 IEnumerable CallsForProperty 我需要找到特定时间段的前 3 个问题，所以我创建了 3 个字典 Dictionary<int, string> FAQfor3Months = null; Dictionary<int, string> FAQfor4to12Months = null; Dictionary<int, string> FAQfor12plusMonths = null; foreach(Activity call in CallsForProperty){   if( /*call is in 3 months*/ ){      //do some unrelated stuff      FAQfor3Months.Add(counter, call.callQuestion)      counter++;   } }我有 2 个问题，我试图找出最常见的 3 个问题，这个查询正确吗？var threeMonthFaqs = FAQfor3Months.GroupBy(x => x.Value).OrderByDescending(x => x.Count()).Take(3);   这也太低效了吧？有没有更好的方法来查询集合？

Answer 1

反转Dictionarys 并计算遇到的每个问题，然后可以使用 LINQ 找出最重要的 3 个问题：

var FAQfor3Months = new Dictionary<string, int>();

var FAQfor4to12Months = new Dictionary<string, int>();

var FAQfor12plusMonths = new Dictionary<string, int>();

foreach (Activity call in CallsForProperty) {

    if ( /*call is in 3 months*/ ) {

        //do some unrelated stuff

        FAQfor3Months.TryGetValue(call.callQuestion, out int count);

        FAQfor3Months[call.callQuestion] = count+1;

    }

}

var top3ThreeMonthFaqs = FAQfor3Months.OrderByDescending(kvp => kvp.Value).Take(3).Select(kvp => kvp.Key).ToList();

Answer 2

您的代码将返回组，而不是实际的问题。尝试这个：

var threeMonthFaqs = FAQfor3Months.Values
                                  .GroupBy(q => q)
                                  .OrderByDescending(g => g.Count())
                                  .SelectMany(g => g)
                                  .Distinct()
                                  .Take(3);