/// <summary>
        /// Sets visiblity of tab item
        /// </summary>
        /// <param name="sheet">Sheet to change property to</param>
        /// <param name="p">Is sheet visible</param>
        protected virtual void SetVisibility(ref SheetControl sheet, bool isVisible)
        {
            if (sheet == null) throw new ArgumentNullException("sheet", "Can't change visiblity of sheet that is null!");

            // Sets control visibility
            sheet.Visibility = isVisible ? System.Windows.Visibility.Visible : System.Windows.Visibility.Hidden;

            if (!isVisible) {
                // TODO: Add tabItem to list of hidden sheets
            }
        }
        /// <summary>
        /// Converts ExcelWorksheet to TabItem sheet equivalent
        /// </summary>
        /// <param name="worksheet">Worksheet to convert, null will create new empty sheet.</param>
        /// <returns>TabItem of given ExcelWorksheet</returns>
        protected TabItem FromExcelWorksheetToTabItem(ExcelWorksheet worksheet = null)
        {
            // Create new TabItem
            TabItem sheet = new TabItem() {
                //Style = (Style)FindResource("SimpleTabItem")
            };

            // Create new SheetControl and fill the information
            SheetControl control = new SheetControl(worksheet);

            // If worksheet isn't null, start importing data
            if (worksheet != null) {
                sheet.Header = worksheet.Name;
                // TODO Import rest
                SetVisibility(ref control, worksheet.Visibility == SheetVisibility.Visible);
            }

            // Sets events
            control.SelectionEnded += (s, se) => {
                UpdateMenuFontSize(se.FontSize);
                ComboBoxFontFamily.SelectedIndex = SystemFontFamilies.IndexOf(se.FontFamily);

                if (se.Formula != null) {

                }
            };

            // Set content to just created control and return tab item
            sheet.Content = control;
            return sheet;
        }