您的代碼會覆蓋現有的動物，因為您沒有為總數創建新的動物new Animal()。
在重復項下方的正確位置獲取重復項總計非常棘手。為此，我將創建一個新類，Animal以便能夠將動物與總數記錄區分開來。
class Animal
{
public string Name { get; set; }
public int Age { get; set; }
public string Gender { get; set; }
}
class AnimalTotals : Animal
{
}
像這樣創建重復的總計：
var duplicateTotals = listAnimals
.GroupBy(a => (a.Name, a.Gender))
.Where(g => g.Count() > 1)
.Select(g => new AnimalTotals {
Name = g.Key.Name,
Age = g.Sum(a => a.Age),
Gender = g.Key.Gender
});
請注意，我使用值元組（在 C# 7.0 中引入）來創建由名稱和性別組成的組鍵。
然后我將重復的總數與現有列表合并，并對結果進行排序以獲得重復項下方的總數。
listAnimals = listAnimals
.Concat(duplicateTotals)
.OrderBy(a => a.Name)
.ThenBy(a => a.Gender)
.ThenBy(a => a is AnimalTotals ? 1 : 0)
.ToList();
有了這個樣本數據
var listAnimals = new List<Animal> {
new Animal{ Name="Ant", Age = 9, Gender = "M" },
new Animal{ Name="Ant", Age = 2, Gender = "M" },
new Animal{ Name="Ant", Age = 5, Gender = "F" },
new Animal{ Name="Ant", Age = 1, Gender = "F" },
new Animal{ Name="Lion", Age = 8, Gender = "M" },
new Animal{ Name="Pig", Age = 1, Gender = "F" },
};
的輸出
foreach (Animal a in listAnimals) {
if (a is AnimalTotals) {
Console.WriteLine($"{a.Name} {a.Gender} totals: {a.Age,4}");
} else {
Console.WriteLine($"{a.Name,-6} {a.Age,2} {a.Gender}");
}
}
是
Ant 5 F
Ant 1 F
Ant F totals: 6
Ant 9 M
Ant 2 M
Ant M totals: 11
Lion 8 M
Pig 1 F
