C# Return different types?

I have a method which returns different types of instances (classes):

public [What Here?] GetAnything()
{
     Hello hello = new Hello();
     Computer computer = new Computer();
     Radio radio = new Radio();

     return radio; or return computer; or return hello //should be possible?!      
}

How can I do this and later work with the variables, e.g. radio.Play(), etc?

Do I need to use generics, and if so, how?

Solution 1:

Here is how you might do it with generics:

public T GetAnything<T>()
{
   T t = //Code to create instance

   return t;
}

But you would have to know what type you wanted returned at design time. And that would mean that you could just call a different method for each creation...

Solution 2:

If there is no common base-type or interface, then public object GetAnything() {...} - but it would usually be preferable to have some kind of abstraction such as a common interface. For example if Hello, Computer and Radio all implemented IFoo, then it could return an IFoo.

Solution 3:

use the dynamic keyword as return type.

 private dynamic getValuesD<T>()
    {
        if (typeof(T) == typeof(int))
        {
            return 0;
        }
        else if (typeof(T) == typeof(string))
        {
            return "";
        }
        else if (typeof(T) == typeof(double))
        {
            return 0;
        }
        else
        {
            return false;
        }
    }

        int res = getValuesD<int>();
        string res1 = getValuesD<string>();
        double res2 = getValuesD<double>();
        bool res3 = getValuesD<bool>();

// dynamic keyword is preferable to use in this case instead of an object type

// because dynamic keyword keeps the underlying structure and data type so that // you can directly inspect and view the value.

// in object type, you have to cast the object to a specific data type to view // the underlying value.

regards,

Abhijit

Solution 4:

Marc's answer should be the correct one, but in .NET 4 you couldn't also go with dynamic type.

This should be used only if you have no control over the classes you return and there are no common ancestors ( usually with interop ) and only if not using dynamic is a lot more painful then using(casting every object in every step :) ).

Few blog post trying to explain when to use dynamic: http://blogs.msdn.com/b/csharpfaq/archive/tags/dynamic/

public dynamic GetSomething()
{
     Hello hello = new Hello();
     Computer computer = new Computer();
     Radio radio = new Radio(); 
     return // anyobject

}