Loading managed dll at runtime and calling a method

Question

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I would like to know, how I can call the methods of the class defined in my dll. The class defined in the dll uses this interface:

C#

interface class ILightControl{
            void Settings();
};

This is the part, where I need to call the method.

C#

System::Reflection::Assembly^ x = System::Reflection::Assembly::LoadFile("C:\\LightControl.dll");
             array<Type^>^t = x->GetTypes();
             Type^InterfaceType;
             Object^obj;
             for(int i = 0; i < t->Length; i++){
                 InterfaceType = t[i]->GetInterface("ILightControl");
                 if(InterfaceType){
                     obj = Activator::CreateInstance(t[i]);
                     //I need to call Settings(); here
                 }
}

How call I now call the method? Thank you very much for your help!

Posted 22-Sep-10 3:58am

egon_ll

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3 solutions

Solution 1

((ILightControl)obj)->Settings();

Posted 22-Sep-10 4:52am

ARopo

Comments

egon_ll 22-Sep-10 11:59am

I have already tried that, but i get the error:

The object of the type LightControl cannot be converted to the type ILightControl.
(LightControl is the name of the class that implements ILightControl in the dll.)

ARopo 23-Sep-10 4:47am

Have you tried
LightControl^ lighcontrol = (LightControl^)obj;
((ILightControl^)lighcontrol)->Settings();

egon_ll 23-Sep-10 5:07am

As LightControl is only defined in the dll, the software doesn't know LightControl at compilation time.

I defined the interface ILightControl in the dll and derived LightControl. I also defined ILightControl in my main program. Now I have to tell the compiler, that the object I created has the function Settings, and call it. This is the first time I'm working with interfaces, so I might overlook something.

egon_ll 23-Sep-10 5:20am

I now tried this:

ILightControl^ilc = dynamic_cast<ilightcontrol^>(obj);
ilc->Settings();

The cast works fine, but when I call the method I get the error:
"Object reference not set to an instance of an object."

I think the problem is, that I'm trying to create an Object of an interface. That is probably not possible.
But as I already have the right object, there must be a possibility to tell the compiler, that the object implements the interface ILightControl, and can therefore call the method Settings().

Solution 2

Try this as a test

<br />
<br />
  LightControl^ lc = (LightControl^)Activator::CreateInstance(LightControl::typeid));<br />
((ILightControl^)lc)->Settings(); <br />

Posted 23-Sep-10 4:53am

ARopo

Comments

egon_ll 23-Sep-10 11:15am

This can not work, as LightControl is only defined in the dll but not in the program calling the dll.
I tried it anyway and I get the error "LightControl not declared".

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ARopo · Accepted Answer · 2010-09-23T22:11:00

Solution 3

In that case I think you may have to call the method using reflection

System::Reflection::MethodInfo^ mi = interfaceType->GetMethod("Settings");
cli::array<System::Object> parameters = gcnew cli::array<System::Object>();
// add any parameter here
System::Object^ retVal = mi->Invoke(obj, parameters)

Posted 23-Sep-10 22:11pm

ARopo

Updated 24-Sep-10 0:02am

v2

Comments

egon_ll 25-Sep-10 5:24am

Thank you! Now it works.

egon_ll 25-Sep-10 5:24am

Reason for my vote of 5
Automatic vote of 5 for accepting answer.