Recipe

1. Add a sample image named monkey.png.
2. In a UIViewController subclass, add class variables for a UIImage and UIImageView.

UIImage _image;
UIImageView _imageView;

3. In the ViewDidLoad method create the UIImage and the UIImageView.

_image = UIImage.FromFile("monkey.png");
_imageView = new UIImageView(new RectangleF(50,50,100,100));
_imageView.ContentMode = UIViewContentMode.ScaleAspectFit;
_imageView.Image = _image;

4. Set the Transform property of the UIImageView and add it as a sub view.

_imageView.Transform = CGAffineTransform.MakeRotation((float)Math.PI/4);            
View.AddSubview (_imageView);

Additional Information

The CGAffineTransform has helper functions to return various affine transforms such as rotation, scale and translation. Setting a CGAffineTransform to the Transform property of a UIView applies the transformation matrix to the view.