How Can Multiple Inheritance Be Simulated in C# and What Are the Alternatives?

Multiple inheritance simulation in C#

Multi -inheritance (one class inherits from multiple parent categories) is usually considered a complex and easy to make mistakes. However, in some cases, it may be beneficial.

Use the interface to simulate more inheritance

C# does not support more inheritance, but can be used to simulate it. The following is an example:

However, the disadvantage of this simulation method is that any interface changes need to be modified

<code class="language-csharp">public interface IFirst { void FirstMethod(); }
public interface ISecond { void SecondMethod(); }

public class First : IFirst { public void FirstMethod() { Console.WriteLine("First"); } }
public class Second : ISecond { public void SecondMethod() { Console.WriteLine("Second"); } }
public class FirstAndSecond : IFirst, ISecond {
    First first = new First();
    Second second = new Second();
    public void FirstMethod() { first.FirstMethod(); }
    public void SecondMethod() { second.SecondMethod(); }
}</code>

.

FirstAndSecond code generation method

Ideally, there should be a way to automatically generate a combination of multiple existing classes. This can be implemented using code generation or fictional C# syntax, as shown below:

Combination alternative

<code class="language-csharp">public class FirstAndSecond : IFirst from First, ISecond from Second { }</code>

Instead of trying to simulate more inheritance, it is better to consider using a combination. The interface can define the combination requirements:

Simplify the expansion method to call

<code class="language-csharp">public interface ISteerable { SteeringWheel wheel { get; set; } }
public interface IBrakable { BrakePedal brake { get; set; } }

public class Vehicle : ISteerable, IBrakable {
    public SteeringWheel wheel { get; set; }
    public BrakePedal brake { get; set; }
    public Vehicle() { wheel = new SteeringWheel(); brake = new BrakePedal(); }
}</code>

Extension method (introduced in C# 3.0) can further simplify the method of hidden attributes call:

Compared with the simulation multiple inheritance, this alternative provides a clearer and more flexible method.

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