base 关键字用于从派生类（子类）中访问基类（父类）的成员：
base调用基类构造函数：
public class father
{
public virtual void Hello(string greeting)
{
Console.WiriteLine(greeting);
}
}
public class son : father
{
public void Start(string greeting):base(greeting)
{
Console.WiriteLine(greeting);
}
}
base在派生类中调用基类的方法：
public class father
{
public virtual void Hello()
{
Console.WiriteLine("Hello");
}
}
public class son : father
{
public void Start()
{
base.Hello();//调用基类的方法,显示Hello
}
}