LAMDA表达式
2017-06-04 17:05 Dirichlet 阅读(264) 评论(0) 编辑 收藏 举报LAMDA表达式
(input parameters) => {statement;}
Lambda 语句的主体可以包含任意数量的语句;但是,实际上通常不会多于两个或三个语句。
通常不必为输入参数指定类型,编译器可以根据委托类型推理,如下:
delegate void TestDelegate(string s, int n); TestDelegate myDel = (s, n )=> { string str = n + " " + "World"; Console.WriteLine(s); n++;}; myDel("Hello", 2);
当然也可以显示指定输入参数的其类型:
delegate void TestDelegate(string s, int n); TestDelegate myDel = (string s, int n )=> { string str = n + " " + "World"; Console.WriteLine(s); n++;}; myDel("Hello", 1);
1. 在LINQ之外使用Lambda表达式,能用匿名方法的地方都可以用Lambda表达式。
public partial class Form1 : Form { public Form1() { InitializeComponent(); // Use a lambda expression to define an event handler. this.Click += (s, e) => { MessageBox.Show(((MouseEventArgs)e).Location.ToString());}; } }
2. 查询中使用Lambda表达式,在where,Linq中使用。
int[] scores = new int[] { 1, 2, 7, 9, 8, 4, 6, 5 }; foreach (var item in scores.Where(n=>n>6)) { Console.WriteLine(item); }
private static void TotalsByGradeLevel() { // This query retrieves the total scores for First Year students, Second Years, and so on. // The outer Sum method uses a lambda in order to specify which numbers to add together. var categories = from student in students group student by student.Year into studentGroup select new { GradeLevel = studentGroup.Key, TotalScore = studentGroup.Sum(s => s.ExamScores.Sum()) }; // Execute the query. foreach (var cat in categories) { Console.WriteLine("Key = {0} Sum = {1}", cat.GradeLevel, cat.TotalScore); } } /* Outputs: Key = SecondYear Sum = 1014 Key = ThirdYear Sum = 964 Key = FirstYear Sum = 1058 Key = FourthYear Sum = 974 */
参考文章:
http://msdn.microsoft.com/zh-cn/library/vstudio/bb397675.aspx