Question

I want a magic to happen like that…

class SomeClass {}

public static void main()

    MagicFunctionOrMacrosOrSomethingThatGetTypeOf("SomeClass") some_var = null;<br />
}

Maybe it’s crazy, but is it possible?
I need it to avoid crazy large switch case, because has a lot of classes, but at certain point of code is unable to tell what of the classes to create.

Let’s have an example:
I have base class:
class baseCLASS {}

have a lot of child classes:
class class1 : baseCLASS {}
class class2 : baseCLASS {}
…
class classn : baseCLASS {}

have some flag that comes from outside to events handler:
string class_name; //actually i use int flag that should have connected with string names in dictionary.

have forced to make this:

   switch(class_name)

   case "class1":
      class1 some_class = new class1();
      some_class.RunHandler();
      break;
   case "class2":
      class2 some_class = new class2();
      some_class.RunHandler();
      break;
   case "classn":
      classn some_class = new classn();
      some_class.RunHandler();
      break;
   }

I want to replace that large switch statement by something like this:

MagicFunctionOrMacrosOrSomethingThatGetTypeOf(class_name) some_var = null;
... some initialization actions with some_var
some_var.Build();
some_var.RunHandler();

oh my…

Answer 1

You have two problems:

1. Given user input, you want to instantiate an object of a varying class. For this, you want a mapping between user input and .NET type name. For the first: you can use a convention — ensure that the type name matches the input; or you can use a Dictionary<string,type>, and populate it; or you can attach an attribute to each class, showing which “verb” it handles. Once you’ve done that, you can use Activator.CreateInstance to (at runtime) create an instance of your unknown class. This returns object.
2. Calling methods on the unknown object. Either define a base class or common interface for the classes (e.g. IRunnable or something), or use dynamic, which gives you duck typing.