csharp/mdict/MainWindow.xaml.cs

using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls;
using mdict.Views;

namespace mdict
{
    public partial class MainWindow : Window
    {
        private readonly Dictionary<string, UserControl> _views = new Dictionary<string, UserControl>();

        public MainWindow()
        {
            InitializeComponent();
            NavigateTo("Search");
        }

        private void Nav_Click(object sender, RoutedEventArgs e)
        {
            if (sender is RadioButton rb && rb.CommandParameter is string viewName)
            {
                NavigateTo(viewName);
            }
        }

        private void NavigateTo(string viewName)
        {
            if (!_views.ContainsKey(viewName))
            {
                switch (viewName)
                {
                    case "Search":
                        _views[viewName] = new SearchView();
                        break;
                    case "Library":
                        _views[viewName] = new LibraryView();
                        break;
                    case "History":
                        _views[viewName] = new HistoryView();
                        break;
                    case "Favorites":
                        _views[viewName] = new FavoritesView();
                        break;
                    case "Settings":
                        _views[viewName] = new SettingsView();
                        break;
                }
            }

            if (_views.TryGetValue(viewName, out var view))
            {
                MainContent.Content = view;
            }
        }
    }
}