using (DotNetGallery.GalleryDataProvider provider = DotNetGallery.GalleryDataProvider.CreateInstance(Context, "~/GalleryFiles/"))
        {
            //get all category
            string[] categoryArray = provider.GetCategoryArray();
            for (int i = 0; i < categoryArray.Length; i++)
            {
                //get id of all categories
                //categoryArray[i] is the category id
                label1.Text += categoryArray[i];
            }
        }