Get all inherited classes of an abstract class [duplicate]

Question

This is such a common problem, especially in GUI applications, that I'm surprised there isn't a BCL class to do this out of the box. Here's how I do it.

public static class ReflectiveEnumerator
{
    static ReflectiveEnumerator() { }

    public static IEnumerable<T> GetEnumerableOfType<T>(params object[] constructorArgs) where T : class, IComparable<T>
    {
        List<T> objects = new List<T>();
        foreach (Type type in 
            Assembly.GetAssembly(typeof(T)).GetTypes()
            .Where(myType => myType.IsClass && !myType.IsAbstract && myType.IsSubclassOf(typeof(T))))
        {
            objects.Add((T)Activator.CreateInstance(type, constructorArgs));
        }
        objects.Sort();
        return objects;
    }
}

A few notes:

• Don't worry about the "cost" of this operation - you're only going to be doing it once (hopefully) and even then it's not as slow as you'd think.
• You need to use Assembly.GetAssembly(typeof(T)) because your base class might be in a different assembly.
• You need to use the criteria type.IsClass and !type.IsAbstract because it'll throw an exception if you try to instantiate an interface or abstract class.
• I like forcing the enumerated classes to implement IComparable so that they can be sorted.
• Your child classes must have identical constructor signatures, otherwise it'll throw an exception. This typically isn't a problem for me.

Assuming they are all defined in the same assembly, you can do:

IEnumerable<AbstractDataExport> exporters = typeof(AbstractDataExport)
    .Assembly.GetTypes()
    .Where(t => t.IsSubclassOf(typeof(AbstractDataExport)) && !t.IsAbstract)
    .Select(t => (AbstractDataExport)Activator.CreateInstance(t));

It may not be the elegant way but you can iterate all classes in the assembly and invoke Type.IsSubclassOf(AbstractDataExport) for each one.

typeof(AbstractDataExport).Assembly tells you an assembly your types are located in (assuming all are in the same).

assembly.GetTypes() gives you all types in that assembly or assembly.GetExportedTypes() gives you types that are public.

Iterating through the types and using type.IsAssignableFrom() gives you whether the type is derived.