Merging two System.Windows.ResourceDictionary into one programmatically in C#

Question

I have an MVVM WPF application and I have below property that loads an xaml dictionary and returns it:

   public static ResourceDictionary ResourceDict
        {
            get
            {
                if (_ResourceDict == null)
                {
                    // Load resource dictionary
                    _ResourceDict = new ResourceDictionary
                    {
                        Source = new Uri("pack://application:,,,/myApp;component/Resources/Dictionary.xaml", UriKind.RelativeOrAbsolute)
                    };

                    return (_ResourceDict);
                }
                else
                {
                    return (_ResourceDict);
                }
            }
        }

Now I need to merge another xaml dictionary (AnotherDictionary.xaml) with above one and return a single ResourceDictionary. How can I do that?