使用LinQ汇总属性值

Question

我有一个名为Product的自定义对象列表：Listclass Product{    string Key1 {get; set;}    string Key2 {get; set;}    int Count1 {get; set;}    int Count2 {get; set;}}我要合并多个产品列表，并且需要创建一个新列表，该列表将具有每个Count属性的总和值。例如List 1:"Key1", "Key2", 1, 2"Key2", "Key3", 3, 4List 2:"Key1", "Key2", 5, 6"Key2", "Key3", 7, 8所以我的新清单应该是：New List:"Key1", "Key2", 6, 8"Key2", "Key3", 10, 12有人可以帮我吗？

Answer 1

你可以这样做

var list1 = new List<Product>()

   {

      new Product(){Key1 = "Key1", Key2 ="Key2", Count1 = 1, Count2 = 2},

      new Product(){Key1 = "Key2", Key2 ="Key3", Count1 = 1, Count2 = 2}

   };

var list2 = new List<Product>()

   {

      new Product(){Key1 = "Key1", Key2 ="Key2", Count1 = 6, Count2 = 8},

      new Product(){Key1 = "Key2", Key2 ="Key3", Count1 = 10, Count2 = 12}

   };

var result = list1.Concat(list2)

                  .GroupBy(x => new {x.Key1,x.Key2})

                  .Select(x => new

                     {

                        x.Key.Key1,

                        x.Key.Key2,

                        SumCount1 = x.Sum(y => y.Count1),

                        SumCount2 = x.Sum(y => y.Count2)

                     }).ToList();

输出

在这里演示

Key1, Key2, 7, 10

Key2, Key3, 11, 14

其他资源

List.AddRange

将指定集合的元素添加到列表的末尾。

Enumerable.GroupBy方法（IEnumerable，Func，Func）

根据指定的键选择器功能对序列的元素进行分组，并使用指定的功能为每个组投影元素。

Enumerable.Concat方法（IEnumerable，IEnumerable）

连接两个序列。

Answer 2

List<Product> lst1 = new List<Product>();

 List<Product> lst2 = new List<Product>();

 lst1.Add(new Product() {Key1 = "K1",Key2 ="K2", Count1 =1, Count2=2 });

 lst1.Add(new Product() { Key1 = "K2", Key2 = "K3", Count1 = 3, Count2 = 4 });

 lst2.Add(new Product() { Key1 = "K1", Key2 = "K2", Count1 = 5, Count2 = 6});

 lst2.Add(new Product() { Key1 = "K2", Key2 = "K3", Count1 = 7, Count2 = 8 });

// Way 1

 var l = lst1.Join(lst2, l1 => l1.Key1, l2 => l2.Key1, 

                (lt1, lt2) => new Product { Key1 = lt1.Key1, Key2 = lt1.Key2, Count1 = lt1.Count1 + lt2.Count1, Count2 = lt1.Count2 + lt2.Count2 } ).ToList() ;

// Way 2

var result = lst1.Join(lst2, x => new { x.Key1, x.Key2 },

                 y => new { y.Key1, y.Key2 }, (x, y) => 

                 new Product { Key1 = x.Key1, Key2 = x.Key2, Count1 = x.Count1 + y.Count1, Count2 = x.Count2 + y.Count2 }).ToList();