请看例子
using System;
namespace _4_5_2
{
/// <summary>
/// Class1 的摘要说明。
/// </summary>
class TestNotPoly
{
/// <summary>
/// 应用程序的主入口点。
/// </summary>
[STAThread]
static void Main(string[] args)
{
TestNotPoly tt=new TestNotPoly();
tt.LoadEmployees();
tt.DoPayroll();
}
protected Employee[] employees;
public void LoadEmployees()
{
employees=new Employee[2];
employees[0]=new ContactEmployee("masathem");
employees[1]=new SalariesEmployee("anubis");
}
public void DoPayroll()
{
for(int i=0;i<employees.GetLength(0);i++)
{
employees[i].CaculatePay();
}
}
}
class Employee
{
public string name;
public Employee(string name)
{
this.name=name;
}
public void CaculatePay()
{
Console.WriteLine("[Employee].CaculatePay() name :{0}",name);
}
}
class SalariesEmployee:Employee
{
public SalariesEmployee(string name):base(name){}
public new void CaculatePay()
{
Console.WriteLine("[SalariesEmployee].CaculatePay() name :{0}",name);
}
}
class ContactEmployee:Employee
{
public ContactEmployee(string name):base(name){}
public new void CaculatePay()
{
Console.WriteLine("[ContactEmployee].CaculatePay() name :{0}",name);
}
}
}
SalariesEmployee 继承自Employe
使用派生类实例化基类对象
employees[0]=new ContactEmployee("masathem");
employees[1]=new SalariesEmployee("anubis");
但employees[]是Employee对象，但是通过“重载”？？却能向下调用派生类的方法？employees[]到底是不是基类对象？
看IL解释
.method public hidebysig instance void LoadEmployees() cil managed
{
// 代码大小 49 (0x31)
.maxstack 4
IL_0000: ldarg.0
IL_0001: ldc.i4.2
IL_0002: newarr _4_5_2.Employee
IL_0007: stfld class _4_5_2.Employee[] _4_5_2.TestNotPoly::employees
IL_000c: ldarg.0
IL_000d: ldfld class _4_5_2.Employee[] _4_5_2.TestNotPoly::employees
IL_0012: ldc.i4.0
IL_0013: ldstr "masathem"
IL_0018: newobj instance void _4_5_2.ContactEmployee::.ctor(string)
IL_001d: stelem.ref
IL_001e: ldarg.0
IL_001f: ldfld class _4_5_2.Employee[] _4_5_2.TestNotPoly::employees
IL_0024: ldc.i4.1
IL_0025: ldstr "anubis"
IL_002a: newobj instance void _4_5_2.SalariesEmployee::.ctor(string)
IL_002f: stelem.ref
IL_0030: ret
} // end of method TestNotPoly::LoadEmployees
荧光笔标记的是派生类的实例构造函数，得到的类为什么能调用此派生类的方法？虽然调用的是派生类来实例化的，但是它终久是基类？基类能调用派生类的方法？