/// <summary>
        /// Forces all images sizes to be refreshed from the respective providers.
        /// </summary>
        protected void RefreshItemImages()
        {
            Size imageSize = ShengToolStripIconImageProvider.GetIconSize(ImageSize);
            ImageScalingSize = imageSize;

            bool changesMade = false;
            IShengToolStripImageProvider imageProvider = null;

            foreach (ToolStripItem item in Items)
            {
                if (item.Size != imageSize)
                {
                    imageProvider = null;

                    // If an image provider was registered with the toolstrip then...
                    if (ContainsImage(item))
                    {
                        if (IsImageSupported(item, ImageSize))
                            item.Image = GetImage(item, ImageSize);
                        else if (UseUnknownImageSizeIcon && IsImageSupported(ImageSize))
                            item.Image = GetImage(ImageSize);

                        changesMade = true;
                    }
                    else if (item is IShengToolStripImageProvider)
                    {
                        imageProvider = item as IShengToolStripImageProvider;
                    }
                    else if (item.Tag is IShengToolStripImageProvider)
                    {
                        imageProvider = item.Tag as IShengToolStripImageProvider;
                    }

                    // If an alternative image provider was found, attempt to use that.
                    if (!changesMade && imageProvider != null)
                    {
                        if (imageProvider.IsImageSupported(ImageSize))
                        {
                            item.Image = imageProvider.GetImage(ImageSize);
                            changesMade = true;
                        }
                    }

                    // Were changes made?
                    if (changesMade)
                    {
                        // Automatically adjust the image scaling mode.
                        if (item.Image != null && item.Image.Size == imageSize)
                            item.ImageScaling = ToolStripItemImageScaling.None;
                        else
                            item.ImageScaling = ToolStripItemImageScaling.SizeToFit;
                    }
                }
            }
        }
        /// <summary>
        /// Assigns an image provider for the specified item.
        /// </summary>
        /// <param name="item">Associated toolstrip item.</param>
        /// <param name="provider">Image provider.</param>
        /// <returns>Returns true when successful.</returns>
        public bool AssignImage(ToolStripItem item, IShengToolStripImageProvider provider)
        {
            if (item == null || provider == null)
                throw new ArgumentException("One or more arguments were null references.");
            if (ContainsImage(item))
                return false;

            ImageProvider.Add(item, provider);
            HasImagesChanged = true;

            if (!IsUpdatingImages)
                RefreshItemImages();

            return true;
        }