/// <summary>
/// Delete existing course
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void DeleteCourse_Click(object sender, RoutedEventArgs e)
{
long id = _courseImagesCache[_selectedLanguage.Name];
_contentManager.DeleteCourse(id);
_courseImagesCache.Remove(_selectedLanguage.Source.ToString());
Courses.Children.Remove(_selectedLanguage);
_selectedLanguage = null;
WrapPanelEducationaLevel.Children.Clear();
WrapPanelGrades.Children.Clear();
NoOfFiles.Text = "";
NoOfLessons.Text = "";
NoOfWeeks.Text = "";
EditCourse.IsEnabled = false;
DeleteCourse.IsEnabled = false;
AddEducationalLevel.IsEnabled = false;
EditEducationalLevel.IsEnabled = false;
DeleteEducationalLevel.IsEnabled = false;
AddGrade.IsEnabled = false;
EditGrade.IsEnabled = false;
DeleteGrade.IsEnabled = false;
EditWeeks.IsEnabled = false;
EditLessons.IsEnabled = false;
EditFiles.IsEnabled = false;
}
