问题
Currently im studying the C# with ASP.NET MVC 4 with Code First Approach. Im Visual Basic Developer, and Now i want to Start C#. And, now i came accross the situation where i've to manage Multiple Inheritance. But, it is not possible with Class i thought. So, how should i manage these classes i have :
//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; }
}
What I want to Make is Approved, ApprovedDate, and ApprovedUserId also common. I want to Specify those Properties like :
public class Approve {
public bool Approved { get; set; }
public DateTime ApprovedDate { get; set; }
public int ApprovedUserId { get; set; }
}
And, want to use like :
public class Student:Person,Approve
{
public DateTime DateOfBirth { get; set; }
public DateTime EnrollmentDate { get; set; }
public string Remarks { get; set; }
}
And, i cannot put those things inside PERSON. Because, i've to use this to another classes to, but those are not Person.
Then, how do i achieve this...
Please give me an Example for the Above Situation.
Please Help. And, Thank You so much in Advance.
回答1:
One possible solution would be to modify your hierarchy:
public class PersonWithApprove : Person { // TODO: replace with non disgusting name
public bool Approved { get; set; }
// etc...
}
public class Student : PersonWithApprove {
}
public class Faculty : PersonWithApprove {
}
Or you could create an interface:
public interface IApprove {
bool Approved { get; set; }
// etc
}
public class Student : Person, IApprove {
}
You might also leave the class Approve as such, and have classes with a property of that type:
public class Student : Person {
Approve _approve = new Approve();
public Approve Approve {
get { return _approve; }
}
}
回答2:
It's a good case, IMHO, to use interfaces here, something like that:
// 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
}
回答3:
Short Answer
Consider using interfaces instead, which allow for multiple inheritance and can be declared using the interface keyword.
Long Answer
Inheritance from multiple base classes in C# is illegal. Classes may only have 1 base class while they can implement any number of interfaces. There are several reasons for this but it mostly comes down to that multiple inheritance introduces much more complexity into a class hierarchy.
Interfaces are used to declare a group of common functionality (methods and properties) that must be implemented by class.
To modify your existing code to use interfaces (instead of multiple inheritance), you can do the following:
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
}
This approach abstracts the implementation of an IApprove interface and, like multiple inheritance, allows the user to operate on objects that implement IApprove yet their concrete type is unknown (or irrelevant).
For more information on the usage of interfaces in C# refer to:
http://msdn.microsoft.com/en-us/library/87d83y5b.aspx
回答4:
Consider the following example , it uses two interfaces :
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();
}
}
回答5:
You can use Composite pattern
public class Student:Person
{
public Approve App { get; set; }
public DateTime DateOfBirth { get; set; }
public DateTime EnrollmentDate { get; set; }
public string Remarks { get; set; }
}
回答6:
Some basic example using the Decorator design pattern:
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;
}
}
}
Demo:
MultipleClass multipleClass = new MultipleClass();
multipleClass.Method1(); //OUTPUT: Class1: Method1, MyInt: 1
multipleClass.Method2(); //OUTPUT: Class2: Method2, MyInt: 1
multipleClass.MyInt = 1;
来源：https://stackoverflow.com/questions/18438196/c-sharp-multiple-inheritance