实例构造函数疑问

新客网 XKER.COM 2004-10-22 来源： 收藏本文

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？

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