//圆角头像_avatarView = new UIImageView(new RectangleF(_blockSpace, _blockSpace, 2 * _avatarRadius, 2 * _avatarRadius));
UIImage img = UIImage.FromFile("profile-pic.jpg");
_avatarView.Layer.Contents = img.CGImage;_avatarView.Layer.MasksToBounds = true;//如果没有将MasksToBounds设置为true，图片圆角无效
_avatarView.Layer.CornerRadius = _avatarRadius;_avatarView.UserInteractionEnabled = true;//用户互动属性()
_avatarView.AddGestureRecognizer(new UITapGestureRecognizer(onClickImage));

 void onClickImage(){try{//UIActionSheet是在iOS弹出的选择按钮项的对话框，可以添加多项，并为每项添加点击事件。//ChangePictureActionSheetDelegate：通过重写UIActionSheetDelegate的Clicked方法，获取当前点击项UIActionSheet _actionSheet = new UIActionSheet("选择图片",new ChangePictureActionSheetDelegate(this,_avatarView), "取消",null, "从相片库", "拍照");                _actionSheet.ShowInView(this.View);}catch (Exception e){Console.WriteLine("Error:" + e.Message);}}

class ChangePictureActionSheetDelegate : UIActionSheetDelegate{UIViewController _controller;UIImageView _img;UIImagePickerController picker;public ChangePictureActionSheetDelegate(UIViewController controller,UIImageView img){_controller = controller;_img = img;}public override void Clicked(UIActionSheet actionSheet, int buttonIndex){Console.WriteLine("你选择了：" + buttonIndex);switch (buttonIndex){case 1: CallPhoto(UIImagePickerControllerSourceType.Camera); break;case 0: CallPhoto(UIImagePickerControllerSourceType.PhotoLibrary); break;default: break;}}        private void CallPhoto(UIImagePickerControllerSourceType type){Console.WriteLine("Begin...");if (UIImagePickerController.IsSourceTypeAvailable(type)){try{picker = new UIImagePickerController();picker.SourceType = type;//允许编辑图片picker.AllowsEditing = true;if (_controller.PresentedViewController == null){_controller.PresentModalViewController(picker, false);}//picker.FinishedPickingImage += picker_FinishedPickingImage;(无效)//AvatarPickerDelegate：通过重写UIImagePickerControllerDelegate的FinishedPickingImage方法获取选择的图片picker.Delegate =new AvatarPickerDelegate(_img);Console.WriteLine("Finished");}catch (Exception e){Console.WriteLine("Error:" + e.Message);}}else{Console.WriteLine("该设备不支持此操作");}}}

class AvatarPickerDelegate:UIImagePickerControllerDelegate {UIImageView _avatar;public AvatarPickerDelegate(UIImageView _imgView) {_avatar = _imgView;}        public override void FinishedPickingImage(UIImagePickerController picker, UIImage image, NSDictionary editingInfo){Console.WriteLine("选择了图片");if (image == null){Console.WriteLine("Null");}//更新显示图片_avatar.Layer.Contents = image.CGImage;//关闭UIImagePickerpicker.DismissModalViewControllerAnimated(true);Console.WriteLine("完成选择");}}