What is the error when creating a custom cell in UICollectionView?

Question

iOS

Here collectionView.DequeueReusableCell("identity", indexPath) as ImageCell the result is always null, but if you cast it to the UICollectionViewCell type, everything is fine and the cell is located. What could be the problem?
ImageCell implementation:

public class ImageCell : UICollectionViewCell
    {
        UIImageView imageView;

        [Export("initWithFrame:")]
        public ImageCell(System.Drawing.RectangleF frame) : base(frame)
        {
            BackgroundView = new UIView { BackgroundColor = UIColor.Orange };

            SelectedBackgroundView = new UIView { BackgroundColor = UIColor.Green };

            ContentView.Layer.BorderColor = UIColor.LightGray.CGColor;
            ContentView.Layer.BorderWidth = 2.0f;
            ContentView.BackgroundColor = UIColor.White;
            ContentView.Transform = CGAffineTransform.MakeScale(0.8f, 0.8f);

            imageView = new UIImageView(UIImage.FromBundle("placeholder.png"));
            imageView.Center = ContentView.Center;
            imageView.Transform = CGAffineTransform.MakeScale(0.7f, 0.7f);

            ContentView.AddSubview(imageView);
        }

        public UIImage Image
        {
            set
            {
                imageView.Image = value;
            }
        }
    }

Спасибо.