Create a derived class from a base class

Declare the new class name followed by a colon and the name of the base class. For example:

class Derived : Base 
{ 
    ... 
}

Call a base class constructor

Supply a constructor parameter list before the body of the derived class constructor. For example:

class Derived : Base 
{ 
    ... 
    public Derived(int x) : Base(x) 
    { 
        ... 
    } 
    ... 
}

Declare a virtual method

Use the virtual keyword when declaring the method. For example:

class Mammal 
{
    public virtual void Breathe() 
    { 
        ... 
    }
    ...
}

Declare an interface

Use the interface keyword. For example:

interface IDemo
{
    string Name();
    string Description(); 
}

Implement an interface

Declare a class using the same syntax as class inheritance, and then implement all the member functions of the interface. For example:

class Test : IDemo 
{ 
    public string IDemo.Name() 
    { 
    ... 
    }
 
    public string IDemo.Description()  
    { 
    ... 
    } 
}