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-   -   Dynamic Assembly Loading (http://www.go4expert.com/showthread.php?t=10119)

Huggz 18Apr2008 21:29
Dynamic Assembly Loading
 
I'm trying to extend my CMS with a plugin interface to make extensibility a little easier to manage. I created 2 classes: an abstract base class (baseModule) containing a single abstract method Init() and a class that inherits from it (TestModule) and throws an exception when Init is called. In my Engine, I'm doing the following:

Code:
            if (!module_dir.Exists) throw new Exception("Modules directory does not exist.");
            foreach (FileInfo f in module_dir.GetFiles("*.dll"))
            {
                Type t = Assembly.LoadFile(f.FullName).GetType();
                baseModule m = Activator.CreateInstance(t) as baseModule;
                if (m == null)
                {
                    throw new Exception("dll is not of type IModule");
                }
                module_list.Add(m);
            }
Unfortunately when I hit Activator.CreateInstance, I get the error :

"No parameterless constructor defined for this object."

Any ideas what I'm doing wrong?

excavator 25Apr2008 17:21
Re: Dynamic Assembly Loading
 
Quote:
Originally Posted by Huggz
I'm trying to extend my CMS with a plugin interface to make extensibility a little easier to manage. I created 2 classes: an abstract base class (baseModule) containing a single abstract method Init() and a class that inherits from it (TestModule) and throws an exception when Init is called. In my Engine, I'm doing the following:

Code:
            if (!module_dir.Exists) throw new Exception("Modules directory does not exist.");
            foreach (FileInfo f in module_dir.GetFiles("*.dll"))
            {
                Type t = Assembly.LoadFile(f.FullName).GetType();
                baseModule m = Activator.CreateInstance(t) as baseModule;
                if (m == null)
                {
                    throw new Exception("dll is not of type IModule");
                }
                module_list.Add(m);
            }
Unfortunately when I hit Activator.CreateInstance, I get the error :

"No parameterless constructor defined for this object."

Any ideas what I'm doing wrong?
it seems that the variable t refer to "System.Reflection.Assembly" not to the dll you want to instantiate. below is a simple sample code about dynamic loading, you need to modify it to fit in your application.

Code:
private void LoadAssembly()
        {
            Assembly a = Assembly.LoadFile(filename);
            System.Type[] sts = a.GetTypes();
            foreach (System.Type st in sts)
            {
                Object o = Activator.CreateInstance(st);
                if (o != null)
                {
                    Console.WriteLine(st.FullName + " Instantiated\n");
                    //proceed with type conversion here
                }
                else
                {
                    Console.WriteLine(st.FullName + " NOT Instantiated\n");
                }
            }                       
        }
hope this help


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