How do I save a BitmapImage from memory into a file in WPF C#?

How do I save a BitmapImage from memory into a file in WPF C#? – Stack Overflow

public static void Save(this BitmapImage image, string filePath)
{
    BitmapEncoder encoder = new PngBitmapEncoder();
    encoder.Frames.Add(BitmapFrame.Create(image));

    using (var fileStream = new System.IO.FileStream(filePath, System.IO.FileMode.Create))
    {
        encoder.Save(fileStream);
    }
}