Code
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
namespace ConsoleApplication1
{
static class Program
{
static void Main(string[] args)
{
//Predicate
//把方法当作参数传递
DisplayProcess(Filter);
//匿名委托
DisplayProcess(delegate(Process process) { return process.WorkingSet64 >= 20 * 1024 * 1024; });
//lambda表达式
DisplayProcess(process => process.WorkingSet64 >= 20 * 1024 * 1024);
//action
Action<string> print_string = (s) => Console.WriteLine(s);
print_string.Invoke("就这么简单!");
//Func
Func<DateTime> get_time = () => DateTime.Now;
DateTime now = get_time.Invoke();
print_string.Invoke(now.ToString());
//扩展方法
List<int> int_list = new List<int> { 1, 2, 3, 4, 5, 6, 7 };
int b= int_list.list_sum();
print_string.Invoke(b.ToString());
//sql中的top和order by
var c = int_list.OrderByDescending(i => i).Take(3);
foreach (int k in c)
{
print_string.Invoke(k.ToString());
}
var d = int_list.OrderByDescending(i => i).Take(3).Sum();
print_string.Invoke(d.ToString());
Console.ReadKey();
}
/// <summary>
/// 扩展方法必须在非泛型静态类中定义
/// </summary>
/// <param name="list"></param>
/// <returns></returns>
static int list_sum(this IEnumerable<int> list)
{
int a = 0;
foreach (var i in list)
{
a += i;
}
return a;
}
/// <summary>
/// Predicate<Process>是泛型委托
/// 定义如下public delegate bool Predicate<T>(T obj);
/// </summary>
/// <param name="match"></param>
private static void DisplayProcess(Predicate<Process> match)
{
foreach(var process in Process.GetProcesses())
{
if (match(process))
{
Console.WriteLine("{0} {1}", process.ProcessName, process.WorkingSet64);
}
}
}
private static bool Filter(Process process)
{
return process.WorkingSet64 >= 20 * 1024 * 1024;
}
}
}
