public class CustomCalendar : Canvas
    {
        public CustomCalendar()
        {
            _grid = new Grid();
            _grid.Width = Width;
            _grid.Height = Height;
            for (int i = 0; i < 8; i++)
                _grid.ColumnDefinitions.Add(new ColumnDefinition());
            for (int i = 0; i < 4; i++)
                _grid.RowDefinitions.Add(new RowDefinition());

            _grid.Children.Add(new Button() { Content = "Тест" });


            this.Children.Add(_grid);
            this.Background = new SolidColorBrush(Color.FromRgb(231, 22, 123));
        }

        private Grid _grid;
    }