Creating an instance with given name?

[juhaka]

Hi!
I have several classes, which inherited the same class and implemented the same interface. And now I want to define in runtime, which instance is created (the name of the class is given in a setting -file).

How I do it? Is there 'Class.forName("xxx&quot' -thing or that...

br.
Juha Ka

 

[xloop]

Don't understand this question..

YourClassInstance.GetType();

????

 

[juhaka]

I mean, I hava an interface,
public interface IFoo{
public void methodA();
}
and I have an abstract class, which implements the interface
public abstract class CFoo:IFoo{
public abstract void methodA();
}.

And then, I have several classes, which inherited this abstract class:
public class MyClass1:CFoo{
void methodA(){
impl_1
}
}

public class MyClass2:CFoo{
void methodA(){
impl_2
}

}

public class MyClass3:CFoo{
void methodA(){
impl_3 }

}

So, I have now three different implementation for IFoo -interface. And now I want define in runtime (via settings -file), which one I use. So, I should create an instance by using the name of the class(MyClass1, MyClass2 or myClass3). I think, it goes like: CFoo myIns = (CFoo)....

Juha Ka

 

[alexboly]

I don't know if there is any way of doing the equivalent of "Class.forName()". But you can implement a factory class that creates an object based on the string you pass as parameter.
You could do this also in the base class, in a static method, something like:

public static MyBaseClass CreateObject(String objectType)
{
if(objectType == "DerivedClass1)
return new DerivedClass1();
....
}

 

[alexboly]

I don't know if there is any way of doing the equivalent of "Class.forName()". But you can implement a factory class that creates an object based on the string you pass as parameter.
You could do this also in the base class, in a static method, something like:

public static MyBaseClass CreateObject(String objectType)
{
if(objectType == "DerivedClass1&quot
return new DerivedClass1();
....
}

 

[xloop]

What are you trying to do?????

 

[juhaka]

My idea is to create a dynamically extendable Windows Service. I'm finding out the way to add a new dll (=new class) without recompile and reinstall the service. Modifying the settings file and restarting the service should be enough.....

Juha Ka

 

[alexboly]

You can use reflection to do that, provided that you have a common interface for the extensions of the service.

 

[juhaka]

Thanks to all, now I know two ways to do that dynamically! But using reflection is easier way, I think.

(Add two namespaces:
using System.Reflection;
using System.Runtime.Remoting;
and, of course, the namespace of CFoo...
....
(in the code)
ObjectHandle objHand = Activator.CreateInstance("DLL-name", "namespace.MyClass3"
CFoo inst = (CFoo)ojbHand.UnWrap())

That's all, now I can dynamically choose which instance I create by changing the parameters of Activator.CreateInstance() -method.

Juha Ka