Question

At the moment, I have this code :

var shellViewLibrary = Assembly.LoadFrom(Path.Combine(_DllsPath, _DllShellView));
IEnumerable<Type> types = shellViewLibrary.GetTypes();

foreach (Type type in types)
{
    var typeIShellViewInterface = type.GetInterface(_NamespaceIShellView, false);
    if (typeIShellViewInterface != null)
    {
        //here
    }
}

The thing is that where I got //here I want to use Activator.CreateInstance to create an object whose type is type in a specific folder (that is outside the build folder)
I tried about 20 different things, most of them with this : http://msdn.microsoft.com/en-us/library/d133hta4.aspx
but none works…
The typical thing I tried is :

object MyObj = Activator.CreateInstance(shellViewLibrary.FullName, type.FullName);

or

object MyObj = Activator.CreateInstance(Path.Combine(_DllsPath, _DllShellView), type.FullName);

I always got different exception, the most common being :

XamlParseException

I feel like that I’m not using Activator.CreateInstance in the right way with 2 parameters. What should I do ?

Answer 1

Once you call this line

var shellViewLibrary = Assembly.LoadFrom(Path.Combine(_DllsPath, _DllShellView)); 

The assembly has been loaded in to memory. So long as you specify types correctly from this then you will be able to use Activator.CreateInstance to create the types. ie: It is not necessary to further specify where the type is.

Regarding Activator, from MSDN the CreateInstance method can accept a System.Type. I would just use this method inside your if-statement:

Activator.CreateInstance(Type type);

What I would try to do to debug this is first create the type and then pass it in to CreateInstance. You may find that the Type creation itself is failing (due to unresolved assembly) or the instantiation of that type (due to exception in the constructor). At first glance your code here appears to be correct:

foreach (Type type in types)      
{          
    var typeIShellViewInterface = type.GetInterface(_NamespaceIShellView, false);          
    if (typeIShellViewInterface != null)          
    {              
        try
        {
            // I assume you are calling this line at the point marked 'here'. 
            // To debug the creation wrap in a try-catch and view the inner exceptions
            var result = Activator.CreateInstance(type);          
        }
        catch(Exception caught)
        {
            // When you hit this line, look at caught inner exceptions
            // I suspect you have a broken Xaml file inside WPF usercontrol
            // or Xaml resource dictionary used by type
            Debugger.Break();
        }
    }      
}  

In your question you specify that you are getting a XamlParseException. It sounds to me like the type in question is a UserControl (or otherwise refers to a WPF Xaml resource file) and there is an error in that Xaml file, i.e. nothing to do with your usage of Assembly.Load or Activator.CreateInstance.

Could you try posting the inner exception(s) to get a better idea on what the problem is?