C#多重继承
本文关键字：多重继承 | 更新日期: 2023-09-27 18:28:57
目前正在使用代码优先的方法研究带有ASP.NET MVC 4的C#。我是Visual Basic开发人员，现在我想启动C#。现在，我遇到了必须管理多重继承的情况。但是，我认为这是不可能的。那么，我应该如何管理我拥有的这些类：
//I have the Following Person Class which Hold Common Properties
//and a Type of Person e.g : Student, Faculty, Administrative
public class Person
{
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string Type { get; set; }
}
//This is my Student Class, which is Derived from Person
public class Student : Person
{
public DateTime DateOfBirth { get; set; }
public DateTime EnrollmentDate { get; set; }
public string Remarks { get; set; }
public bool Approved { get; set; }
public DateTime ApprovedDate { get; set; }
public int ApprovedUserId { get; set; }
}
//This is my Faculty Class, which is also Derived from Person
public class Faculty : Person
{
public DateTime HiredDate { get; set; }
public bool Approved { get; set; }
public DateTime ApprovedDate { get; set; }
public int ApprovedUserId { get; set; }
}
我想做的是Approved、ApprovedDate和ApprovedUserId也很常见。我想指定那些属性，如：
public class Approve {
public bool Approved { get; set; }
public DateTime ApprovedDate { get; set; }
public int ApprovedUserId { get; set; }
}
并且，想要使用类似：
public class Student : Person, Approve
{
public DateTime DateOfBirth { get; set; }
public DateTime EnrollmentDate { get; set; }
public string Remarks { get; set; }
}
而且，我不能把这些东西放在PERSON里面。因为，我不得不用这个来给另一个类，但那些不是Person。
那么，我该如何做到这一点。。。
请给我举一个上述情况的例子。
请帮忙。而且，非常感谢你提前。
一个可能的解决方案是修改层次结构：
public class PersonWithApprove : Person { // TODO: replace with non disgusting name
public bool Approved { get; set; }
// etc...
}
public class Student : PersonWithApprove {
}
public class Faculty : PersonWithApprove {
}
或者你可以创建一个接口：
public interface IApprove {
bool Approved { get; set; }
// etc
}
public class Student : Person, IApprove {
}
您也可以将类Approve保留为这样，并使类具有该类型的属性：
public class Student : Person {
Approve _approve = new Approve();
public Approve Approve {
get { return _approve; }
}
}
IMHO，在这里使用接口是一个很好的例子，类似于
// Interfaces:
// General person
public interface IPerson {
int Id { get; set; }
string FirstName { get; set; }
string LastName { get; set; }
string Type { get; set; }
}
// Approvable person
public interface IApprovable {
bool Approved { get; set; }
DateTime ApprovedDate { get; set; }
int ApprovedUserId { get; set; }
}
// Student is a IPerson + IApprovable
public interface IStudent: IPerson, IApprovable {
DateTime DateOfBirth { get; set; }
DateTime EnrollmentDate { get; set; }
}
// So classes will be
public class Approve: IApprovable {
... //TODO: Implement IApprovable interface here
}
public class Faculty: IPerson, IApprovable {
public DateTime HiredDate { get; set; }
... //TODO: Implement IPerson interface here
... //TODO: Implement IApprovable interface here
}
public class Student: IStudent {
public string Remarks { get; set; }
... //TODO: Implement IStudent interface here
}
简短回答
请考虑使用接口，它允许多重继承，并且可以使用interface关键字声明。
长答案
从C#中的多个基类继承是非法的。类可能只有一个基类，而它们可以实现任意数量的接口。这有几个原因，但主要是因为多重继承给类层次结构引入了更多的复杂性。
接口用于声明一组必须由类实现的通用功能（方法和属性）。
要修改现有代码以使用接口（而不是多重继承），可以执行以下操作：
public interface IApprove // Defines a set of functionality that a class must implement.
{
// All these properties must be inherited as public when implemented.
bool Approved { get; set; } // Property declaration.
DateTime ApprovedDate { get; set; }
int ApprovedUserId { get; set; }
}
public class Student : Person, IApprove
{
public DateTime DateOfBirth { get; set; }
public DateTime EnrollmentDate { get; set; }
public string Remarks { get; set; }
#region IApprove Implementation
private bool _approved; // Private variable that is accessed through the 'Approved' property of the 'IApprove' interface.
public bool Approved // Defines 'Approved' inherited from IApprove
{
get { return _approved; }
set { _approved = value; }
}
private DateTime _approvedDate;
public DateTime ApprovedDate // Defines 'ApprovedDate' inherited from IApprove.
{
get { return _approvedDate; }
set { _approvedDate = value; }
}
private int _approvedUserId;
public int IApprove.ApprovedUserId // Alternative syntax to define an interfaces property.
{
get { return _approvedUserId; }
set { _approvedUserId = value; }
}
#endregion
}
这种方法抽象了IApprove接口的实现，并且与多重继承一样，允许用户对实现IApprove但其具体类型未知（或不相关）的对象进行操作。
有关C#中接口使用的更多信息，请参阅：
http://msdn.microsoft.com/en-us/library/87d83y5b.aspx
考虑以下示例，它使用两个接口：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
////////
////////
/// Multiple Inheritance With Interfaces
public interface Interface1
{
void func1();
void fun();
}
public interface Interface2
{
void func2();
void fun();
}
public class MyTestBaseClass : Interface1, Interface2
{
void Interface1.func1()
{
Console.WriteLine("From MyInterface1 Function()");
return;
}
void Interface2.func2()
{
Console.WriteLine("From MyInterface2 Function()");
return;
}
void Interface1.fun()
{
Console.WriteLine("fun1()");
}
void Interface2.fun()
{
Console.WriteLine("fun2()");
}
public static void Main()
{
MyTestBaseClass myclass = new MyTestBaseClass();
((Interface1)myclass).func1();
((Interface2)myclass).func2();
}
}
您可以使用复合模式
public class Student:Person
{
public Approve App { get; set; }
public DateTime DateOfBirth { get; set; }
public DateTime EnrollmentDate { get; set; }
public string Remarks { get; set; }
}
使用Decorator设计模式的一些基本示例：
public class Class1
{
public void Method1()
{
Console.write($"Class1: Method1, MyInt: {MyInt}");
}
public int MyInt { get; set; }
}
public class Class2
{
public void Method2()
{
Console.write($"Class2: Method2, MyInt: {MyInt}");
}
public int MyInt { get; set; }
}
public class MultipleClass
{
private Class1 class1 = new Class1();
private Class2 class2 = new Class2();
public void Method1()
{
class1.Method1();
}
public void Method2()
{
class2.Method2();
}
private int _myInt;
public int MyInt
{
get { return this._myInt; }
set
{
this._myInt = value;
class1.MyInt = value;
class2.MyInt = value;
}
}
}
演示：
MultipleClass multipleClass = new MultipleClass();
multipleClass.Method1(); //OUTPUT: Class1: Method1, MyInt: 1
multipleClass.Method2(); //OUTPUT: Class2: Method2, MyInt: 1
multipleClass.MyInt = 1;