Is it possible to extend 2 classes at once?

Question

I have these classes :

public class myClassPage : System.Web.UI.Page
{
    public myClassPage ()
    {
    
    }
}

public class myClassControl : System.Web.UI.UserControl
{
    public myClassControl ()
    {
    
    }
}

and I'd like have another Class that extends these classes, something like this :

public class myClassData : myClassPage, myClassControl
{
    public myClassData ()
    {
    
    }
}

is it possible to do this or is there something else I could do?

Answer 1

In the case where you need to extend two classes, you might be served to favor composition over inheritance, and to use interfaces as other answers have mentioned. An example:

Start by definining your interfaces

interface IFoo 
{
    void A(); 
}

interface IBar
{
    void B();
}

Then create concrete classes that implement each interface

class Foo : IFoo
{
    public void A()
    {
         // code
    }
}

class Bar : IBar 
{
    public void B()
    {
         // code 
    }
}

Finally, in the class you want to exhibit both sets of behaviors, you can implement each interface but compose the implementations with the concrete classes.

public class Baz : IFoo, IBar
{
    IFoo foo = new Foo(); // or inject 
    IBar bar = new Bar(); // or inject

    public void A()
    {
        foo.A();
    }

    public void B()
    {
        bar.B();
    }
}

Answer 2

This is called Multiple Inheritance. You can find more information on Wikipedia - Multiple inheritance regarding the subject.

Multiple inheritance is supported in some langages:

Languages that support multiple inheritance include: C++, Common Lisp, Curl, Dylan, Eiffel, Logtalk, Object REXX, Scala, OCaml, Perl, Perl 6, POP-11, Python, and Tcl

In C#, interfaces can be used for mimicking multiple inheritance:

Some object-oriented languages, such as C#, Java, and Ruby implement single inheritance, although interfaces provide some of the functionality of true multiple inheritance.

Example:

public class myClassData : myClassPageInterface, myClassControlInterface 
{
    // ...
}