C# 一个继承

为什么下面程序 按F5能运行 而按 ctrl+F5就会有错误

using System;
using System.Collections.Generic;
using System.Text;

namespace 继承
{
class grandfather
{

public grandfather()
{
Console.WriteLine("grandfather");
}

public void son()
{
Console.WriteLine("son");
}
}

class father:grandfather
{


public father()
{

Console.WriteLine("father");

}

}
class Program
{
static void Main(string[] args)
{
father f = new father();
f.son();
Console.ReadLine();

}
}
}