c# - 何时使用委托(delegate)而不是接口(interface)

Question

根据这个article ，它说:

Use a delegate in the following circumstances:

• A class may need more than one implementation of the method.

Use an interface in the following circumstances:

• A class only needs one implementation of the method.

有人能给我解释一下吗？

Answer 1

A class may need more than one implementation of the method.

public delegate int PerformCalculation(int x, int y);

void SomeMethod()
{
    PerformCalculation PerformCalculation_1 = myDelegateFun_1;
    PerformCalculation PerformCalculation_2 = myDelegateFun_2;
    PerformCalculation_1(5, 3);
    PerformCalculation_2(5, 3);      
}

private int myDelegateFun_1(int x, int y)
{
    return x + y;
}
private int myDelegateFun_2(int x, int y)
{
    return x + y;
}

上面例子中的PerformCalculation_1、PerformCalculation_2是PerformCalculation的多重实现

A class only needs one implementation of the method

interface IDimensions 
{
   float Length();
}

class Box : IDimensions 
{
   float Length() 
   {
       return lengthInches;
   }
}

在上面的示例中，接口(interface)公开的方法只有一个实现。