利用委托和递归计算两个数之间所有数字的和？
class Program
{static void Main(string[] args)
{
Func<int, int, int, int> Sum = null;
Sum = (start, end, result) =>
{
if (start > end)
{
return result;
}
return Sum(start + 1, end, result + start);
};
Console.WriteLine(Sum(0, 5, 0));
Console.ReadKey();
}
}