Question

asp.net中override是什么意思，什么时候可以用？有什么作用？

Answer 1

一般是实现虚方法的时候需要的关键字 [虚方法声明关键字virtual]
要扩展或修改继承的方法、属性、索引器或事件的抽象实现或虚实现，必须使用 override 修饰符
比如：
class TestOverride
{
public class Employee
{
public string name;

// Basepay is defined as protected, so that it may be
// accessed only by this class and derrived classes.
protected decimal basepay;

// Constructor to set the name and basepay values.
public Employee(string name, decimal basepay)
{
this.name = name;
this.basepay = basepay;
}

// Declared virtual so it can be overridden.
public virtual decimal CalculatePay()
{
return basepay;
}
}

// Derive a new class from Employee.
public class SalesEmployee : Employee
{
// New field that will affect the base pay.
private decimal salesbonus;

// The constructor calls the base-class version, and
// initializes the salesbonus field.
public SalesEmployee(string name, decimal basepay,
decimal salesbonus) : base(name, basepay)
{
this.salesbonus = salesbonus;
}

// Override the CalculatePay method
// to take bonus into account.
public override decimal CalculatePay()
{
return basepay + salesbonus;
}
}
}
详情参阅：http://msdn.microsoft.com/zh-cn/library/ebca9ah3%28VS.80%29.aspx