private static IEnumerable<Form> LoadFormsFromAssembly(string fileName)
{
    Assembly asm = Assembly.LoadFrom(fileName);
    foreach (Type type in asm.GetExportedTypes()) {
        if (typeof(Form).IsAssignableFrom(type) &&
           (type.Attributes & TypeAttributes.Abstract) != TypeAttributes.Abstract) {
            Form form = (Form)Activator.CreateInstance(type);
            yield return form;
        }
    }
}