如何使用Linq從物件串列中獲取最大計數和最小計數

我需要根據月份對其進行分組并獲得最大和最小計數。聽說，Sep Month 有 Max count 而 Jun Month 有 Min count。所以我需要最大值為5，最小值為1。

提前致謝。

public class Test
            {
            public string Month { get; set; }
            public string ID { get; set; }
            public string SubMonth { get; set; }

            }

            List<Test> test = new List<Test>();

            test.Add(new Test { Month = "Sep", ID ="1",  SubMonth = "Sep2" });
            test.Add(new Test { Month = "Sep", ID = "1", SubMonth = "Sep3" });
            test.Add(new Test { Month = "Sep", ID = "1", SubMonth = "Sep4" });
            test.Add(new Test { Month = "Sep", ID = "1", SubMonth = "Sep5" });
            test.Add(new Test { Month = "Sep", ID = "1", SubMonth = "Sep6" });

            test.Add(new Test { Month = "Jun", ID = "3", SubMonth = "Jun2" });


            test.Add(new Test { Month = "Jul", ID = "4", SubMonth = "Jul2" });
            test.Add(new Test { Month = "Jul", ID = "4", SubMonth = "Jul3" });

            test.Add(new Test { Month = "Jan", ID = "5", SubMonth = "Jan2" });
            test.Add(new Test { Month = "Jan", ID = "5", SubMonth = "Jan3" });
            test.Add(new Test { Month = "Jan", ID = "5", SubMonth = "Jan4" });
            test.Add(new Test { Month = "Jan", ID = "5", SubMonth = "Jan5" });

uj5u.com熱心網友回復：

你可以這樣做。您將獲得最大和最小計數：

var result = (test.GroupBy(item => item.Month)
                        .Select(itemGroup => new { Item = itemGroup.Key, Count = itemGroup.Count() })
                        .OrderByDescending(Item => Item.Count).ThenBy(Item => Item.Item)
                     ).ToList(); 
        Console.WriteLine("{0} {1}\r\n{2} {3}", result.First().Item, result.First().Count, result.Last().Item, result.Last().Count);

uj5u.com熱心網友回復：

使用linq你可以這樣做。

var sepCount = test.Where(x => x.Month == "Sep").Count();
var junCount = test.Where(x => x.Month == "Jun").Count();
// you can get the count of each month in the list
var monthCount = test.GroupBy(x => x.Month).ToList().Select(x => x.Count()).ToList();

uj5u.com熱心網友回復：

如果您只想要最小和最大計數，您可以使用Aggregate元組來收集它們：

var minmax = test.GroupBy(t => t.Month)
                 .Select(tg => new { Month = tg.Key, Count = tg.Count() })
                 .Aggregate((Min: int.MaxValue, Max: int.MinValue), (mm, mc) => ((mc.Count < mm.Min ? mc.Count : mm.Min), (mc.Count > mm.Max ? mc.Count : mm.Max)));

如果您還想知道最小和最大月份，您還需要將其保存在元組中：

var minmaxMonth = test.GroupBy(t => t.Month)
                      .Select(tg => new { Month = tg.Key, Count = tg.Count() })
                      .Aggregate((Min: new { Month = "Min", Count = int.MaxValue }, Max: new { Month = "Max", Count = int.MinValue }),
                                 (mm, mc) => ((mc.Count < mm.Min.Count ? mc : mm.Min), (mc.Count > mm.Max.Count ? mc : mm.Max)));

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