LINQ中的聚合函数

在LINQ中，聚合函数是用于从值的集合中计算单个值的那些函数。聚合函数的现实示例是根据全年收集的读数来计算2018年发生的年降雨量。另一个示例，sum函数用于查找给定数组或序列中存在的值的总和。

以下是用于执行聚合操作的方法的列表：

Method	Description
Aggregate	It performs, a custom aggregation operation on the values of a collection.
Average	It calculates the average value of a collection of values.
Count	It counts the elements in a collection, optionally only those elements that satisfy a predicate function.
LongCount	It counts the elements in a large collection, optionally only those elements that satisfy a predicate function.
Max	It determines the maximum value in a collection.
Min	It determines the minimum value in a collection.
Sum	It calculates the sum of the values in a collection.

范例1：

// C# program to illustrate how to
// find the sum of the given sequence
using System;
using System.Linq;
  
public class GFG {
  
    // Main Method
    static public void Main()
    {
  
        int[] sequence = {20, 40, 50, 68, 90, 
                          89, 99, 9, 57, 69};
  
        Console.WriteLine("The sum of the given sequence is: ");
  
        // Finding sum of the given sequence
        // Using Sum function
        int result = sequence.Sum();
        Console.WriteLine(result);
    }
}

输出：

The sum of the given sequence is: 
591

范例2：

// C# program to illustrate how to 
// find the minimum and maximum value
// from the given sequence
using System;
using System.Linq;
  
public class GFG {
  
    // Main Method
    static public void Main()
    {
  
        int[] sequence = {201, 39, 50, 9, 7, 99};
  
        // Display the Sequence
        Console.WriteLine("Sequence is: ");
  
        foreach(int s in sequence)
        {
            Console.WriteLine(s);
        }
  
        // Finding the minimum value
        // from the given sequence
        // Using Min function
        int result1 = sequence.Min();
  
        Console.WriteLine("Minimum Value is: {0}", result1);
  
        // Finding the maximum value 
        // from the given sequence
        // Using Max function
        int result2 = sequence.Max();
  
        Console.WriteLine("Maximum Value is: {0}", result2);
    }
}

输出：

Sequence is: 
201
39
50
9
7
99
Minimum Value is: 7
Maximum Value is: 201

参考：

• https://docs.microsoft.com/zh-cn/dotnet/csharp/programming-guide/concepts/linq/aggregation-operations