How to get an object from a loaded dll

Question

I see this question a fair amount on SO, and I've followed that advice, but I appear to be doing something wrong. The dll seems to load in fine but the object CreateInstance is returning is null.

I have this dll:

namespace Backfill
{
public class Module : Kernel.Module
{
    public override void ModuleStart()
    {
        //Stuff
    }
}
}

In another DLL with a DIFFERENT namespace

namespace Kernel
{

public abstract class Module
{
    public abstract void ModuleStart();
}



public static void KernelStart()
    {
        string load_dll = @"Path to DLL";

        Assembly test_dll = Assembly.LoadFile(load_dll + ".dll");

        Module test_mod = (Module)test_dll.CreateInstance("Kernel.Module");

        test_mod.ModuleStart();
    }
}

(Module)test_dll.CreateInstance("Kernel.Module"); is returning null, though. Any idea why?

Is the concrete class in the first dll also in the `Kernel` namespace? — antonijn, Feb 14 '13 at 20:45
@Antonijn Ah yes, I should have specified, the first dll is in a completely different namespace and references `Kernel` library to inherit the `Module` class. — cost, Feb 14 '13 at 20:59
@Antonijn The namespace is `Backfill`. Ooooh so would I pass it "Backfill.Module" to fix this? — cost, Feb 14 '13 at 21:02

score 4 · Accepted Answer · answered Feb 14 '13 at 21:03

(Module)test_dll.CreateInstance("Kernel.Module")

This won't work. As you specified, the Module class which you're trying to instantiate (which, I assume, is the one from the first DLL), is not in the Kernel namespace, but in the Backfill namespace. You should therefore have something along these lines:

(Module)test_dll.CreateInstance("Backfill.Module")

score 2 · Answer 2 · edited May 23 '17 at 12:27

2

Kernel.Module is an abstract class. You cannot create an instance of it directly. You need to create an instance of the derived class.

Edit: Since supplying more info:

@Antonijn has the same answer. You need to specify the type that you want directly. BackFill.Module seems like the correct one.

Before Edit:

If you have the same names in multiple assemblies then yo need to use a fully qualified (including assembly name) for the type you want. For exmaple: https://stackoverflow.com/a/2300428/30225 as an possible answer.

edited May 23 '17 at 12:27

Community

1
1

answered Feb 14 '13 at 20:53

Preet Sangha

64,563
18
145
216

1

I didn't specify, sorry, the first dll is in a separate namespace and only references the Kernel library in order to inherit Module. In this case then, how would I make an instance of the derived class in the newly loaded DLL? – cost Feb 14 '13 at 21:01

How to get an object from a loaded dll

2 Answers2