LINQ 学习路程 -- 查询操作 Aggregate
2024-10-19 14:53:49
聚合操作执行数学的运算，如平均数、合计、总数、最大值、最小值
| Method | Description |
|---|---|
| Aggregate | 在集合上执行自定义聚集操作 |
| Average | 求平均数 |
| Count | 求集合的总数 |
| LongCount | 求集合的总数 |
| Max | 最大值 |
| Min | 最小值 |
| Sum | 总数 |
public static TSource Aggregate<TSource>(this IEnumerable<TSource> source,
Func<TSource, TSource, TSource> func); public static TAccumulate Aggregate<TSource, TAccumulate>(this IEnumerable<TSource> source,
TAccumulate seed,
Func<TAccumulate, TSource, TAccumulate> func); public static TResult Aggregate<TSource, TAccumulate, TResult>(this IEnumerable<TSource> source,
TAccumulate seed,
Func<TAccumulate, TSource, TAccumulate> func,
Func<TAccumulate, TResult> resultSelector);
Aggregate接受2个参数，一般第一个参数是称为累积数（默认情况下等于第一个值），而第二个代表了下一个值。第一次计算之后，计算的结果会替换掉第一个参数，继续参与下一次计算。
public static TAccumulate Aggregate<TSource, TAccumulate>(this IEnumerable<TSource> source,
TAccumulate seed,
Func<TAccumulate, TSource, TAccumulate> func);
seed作为种子值进行累加
// Student collection
IList<Student> studentList = new List<Student>>() {
new Student() { StudentID = , StudentName = "John", Age = } ,
new Student() { StudentID = , StudentName = "Moin", Age = } ,
new Student() { StudentID = , StudentName = "Bill", Age = } ,
new Student() { StudentID = , StudentName = "Ram" , Age = } ,
new Student() { StudentID = , StudentName = "Ron" , Age = }
}; string commaSeparatedStudentNames = studentList.Aggregate<Student, string>(
"Student Names: ", // seed value
(str, s) => str += s.StudentName + "," ); Console.WriteLine(commaSeparatedStudentNames);
第三个参数对结果进行构造返回
public static TResult Aggregate<TSource, TAccumulate, TResult>(this IEnumerable<TSource> source,
TAccumulate seed,
Func<TAccumulate, TSource, TAccumulate> func,
Func<TAccumulate, TResult> resultSelector);
IList<Student> studentList = new List<Student>>() {
new Student() { StudentID = , StudentName = "John", Age = } ,
new Student() { StudentID = , StudentName = "Moin", Age = } ,
new Student() { StudentID = , StudentName = "Bill", Age = } ,
new Student() { StudentID = , StudentName = "Ram" , Age = } ,
new Student() { StudentID = , StudentName = "Ron" , Age = }
};
string commaSeparatedStudentNames = studentList.Aggregate<Student, string,string>(
String.Empty, // seed value
(str, s) => str += s.StudentName + ",", // returns result using seed value, String.Empty goes to lambda expression as str
str => str.Substring(,str.Length - )); // result selector that removes last comma
Console.WriteLine(commaSeparatedStudentNames);
最新文章
- MooseFS学习-概述
- web组件
- Integrating JAD decompiler into JDeveloper(转)
- Search a 2D Matrix | & II
- 实验八--uart
- vojis1523 NOI2002 贪吃的九头龙
- C# 1作业 2广场砖面积 护栏长度
- Myeclipse 常用操作（待补充）
- List<bean>转换Jsonarray知识心得
- 我的第一个spring_boot项目
- Docker应用：Kubernetes（容器集群）
- TP5.x——update更新成功但是返回是0
- JavaFX 简介
- Java编程基础篇第六章
- MP实战系列(一)之入门框架搭建和使用
- I - 取石子游戏
- uvm设计分析——field automation
- BeautifulSoup 模块详解
- dp——poj1088（Description）
- [leetcode]449. Serialize and Deserialize BST序列化反序列化二叉搜索树(尽量紧凑)