Func<int,bool> f2=delegate(int i)
{
return i>5;
};
Console.WriteLine(f2(9));
Func<int,bool>f22=i=>i>5;
Console.WriteLine(f22(2));
int[] num = new int[]{3,8,9,15,34,39 };
//IEnumerable<int> result= num.Where(i => i>10);
//IEnumerable<int> result = MyWhere2(num, a => a > 10);
//C# var定义的变量为类型推断,此处根据函数返回值,推断result 为List<int>
var result = MyWhere2(num, a => a > 10);
foreach (int i in result)
{
Console.WriteLine(i);
}
//IEnumerable是可枚举类型,一般在迭代时应用广泛,如foreach中要循环访问的集合或数组都实现了IEnumerable接口。只要能够遍历,都直接或间接实现了IEnumerable接口。
static IEnumerable<int> MyWhere(IEnumerable<int> items,Func<int,bool> f)
{
List<int> result = new List<int>();
foreach (var item in items)
{
if(f(item)==true)
result.Add(item);
}
return result;
}
static IEnumerable<int> MyWhere2(IEnumerable<int> items, Func<int, bool> f)
{
//List<int> result = new List<int>();
foreach (var item in items)
{
if (f(item) == true)
yield return item;
//result.Add(item);
}
// return result;
}