List中常用的linq操作

 1  [Serializable]
 2     public class Product
 3     {
 4         public Product()
 5         {
 6           
 7         
 8         }
 9 
10         public Product(string id,string pname,int num,double price)
11         {
12             this.ProductID = id;
13             this.ProductName = pname;
14             this.Num = num;
15             this.Price = price;
16         }
17         public string ProductID { get; set; }
18         public string ProductName { get; set; }
19         public int Num { get; set; }
20         public double Price { get; set; }
21    
22 
23     }

初始化

1 List<Product> plist = new List<Product>()
2             {
3                 new Product{ ProductID="01",ProductName ="牛奶",Num=45,Price=4.0 },
4                 new Product{ ProductID="02",ProductName ="饼干",Num=8,Price=8.5 },
5                 new Product{ ProductID="03",ProductName ="糖果",Num=9,Price=2.1 },
6                 new Product{ ProductID="04",ProductName ="饮料",Num=10,Price=3.5 },
7             };

1.使用linq获取list集合中的某个字段值的集合

double[] Prices = plist.Select(u => u.Price).ToArray();

2.使用linq求list集合中所有对象price字段的和

var Price_sum = plist.Sum(u => u.Price)

求数量*单价的和

var Price_sum = plist.Sum(u => u.Price)