private void SearchButton_Click(object sender, RoutedEventArgs e)
        {
            var text     = KeywordTextBox.Text;
            var keywords = text.Split(new string[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries);

            var list = new List <string>();

            for (var i = 0; i < keywords.Length; i++)
            {
                list.Add(keywords[i].Replace(" ", string.Empty));
            }

            var exercises = ExerciseManager.Filter(list);

            ExerciseListBox.ItemsSource = exercises;
        }