功能优化：重构更新弹窗交互逻辑，支持显示日志与手动下载；修复并发检测问题

Author: claude

Dialogs/ViewModels/AboutViewModel.cs

@@ -24,6 +24,8 @@ public AboutViewModel() : this(new UpdateService())
     [RelayCommand]
     private async Task OnCheckUpdateAsync()
     {
+        if (UpdateViewModel.IsUpdateDialogOpen) return;
+
         IsCheckingUpdate = true;
         try
         {

Dialogs/ViewModels/UpdateViewModel.cs

@@ -14,6 +14,8 @@ namespace ProxyChecker.Dialogs.ViewModels;
 
 public partial class UpdateViewModel : ObservableObject, IDialogContext
 {
+    public static bool IsUpdateDialogOpen { get; set; }
+
     private readonly UpdateService _updateService;
     private UpdateInfo? _updateInfo;
     private CancellationTokenSource? _cts;
@@ -24,6 +26,8 @@ public partial class UpdateViewModel : ObservableObject, IDialogContext
     [NotifyCanExecuteChangedFor(nameof(StartCommand), nameof(StopCommand), nameof(RestartCommand))]
     private DownloadStatus _status = DownloadStatus.NotStarted;
 
+    [ObservableProperty] private string? _releaseNotes;
+
     // Design-time constructor
     public UpdateViewModel()
     {
@@ -39,8 +43,7 @@ public UpdateViewModel(UpdateService updateService, UpdateInfo? updateInfo = nul
         if (_updateInfo != null)
         {
             Statistics.Version = _updateInfo.TargetFullRelease.Version.ToString();
-            // 直接开始下载，UpdateService 已在 AboutViewModel 中初始化
-            _ = StartAsync();
+            ReleaseNotes = _updateInfo.TargetFullRelease.NotesMarkdown;
         }
         else
         {
@@ -58,8 +61,7 @@ private async Task CheckUpdatesAsync()
             if (_updateInfo != null)
             {
                 Statistics.Version = _updateInfo.TargetFullRelease.Version.ToString();
-                // Auto start download if update is found, as we are in the UpdateDialog
-                await StartAsync();
+                ReleaseNotes = _updateInfo.TargetFullRelease.NotesMarkdown;
             }
             else
             {

Dialogs/Views/UpdateDialog.axaml

@@ -68,8 +68,31 @@
             <Run Text="版本更新" />
         </SelectableTextBlock>
 
+        <!-- Release Notes -->
+        <Border Height="150"
+                Width="400"
+                Background="{DynamicResource SemiColorFill0}"
+                CornerRadius="6"
+                Padding="10"
+                IsVisible="{Binding Status,
+                            Converter={StaticResource EnumToBooleanConverter},
+                            ConverterParameter={x:Static models:DownloadStatus.NotStarted},
+                            Mode=OneWay}">
+            <ScrollViewer>
+                <SelectableTextBlock Text="{Binding ReleaseNotes}" TextWrapping="Wrap" />
+            </ScrollViewer>
+        </Border>
+
         <!-- Status Text -->
         <Panel>
+            <SelectableTextBlock
+                HorizontalAlignment="Center"
+                IsVisible="{Binding Status,
+                            Converter={StaticResource EnumToBooleanConverter},
+                            ConverterParameter={x:Static models:DownloadStatus.NotStarted},
+                            Mode=OneWay}"
+                Text="发现新版本，是否立即更新？" />
+
             <SelectableTextBlock
                 HorizontalAlignment="Center"
                 IsVisible="{Binding Status,
@@ -98,6 +121,26 @@
         <!-- Controls -->
         <StackPanel Orientation="Horizontal" Spacing="10" HorizontalAlignment="Center">
 
+            <!-- Start Update -->
+            <Button
+                Content="立即更新"
+                Classes="Primary"
+                Command="{Binding StartCommand}"
+                IsVisible="{Binding Status,
+                            Converter={StaticResource EnumToBooleanConverter},
+                            ConverterParameter={x:Static models:DownloadStatus.NotStarted},
+                            Mode=OneWay}" />
+
+            <!-- Cancel Update -->
+            <Button
+                Content="暂不更新"
+                Classes="Secondary"
+                Command="{Binding CloseCommand}"
+                IsVisible="{Binding Status,
+                            Converter={StaticResource EnumToBooleanConverter},
+                            ConverterParameter={x:Static models:DownloadStatus.NotStarted},
+                            Mode=OneWay}" />
+
             <!-- Stop / Cancel -->
             <u:IconButton
                 Name="StopButton"

Dialogs/Views/UpdateDialog.axaml.cs

@@ -1,5 +1,7 @@
 using Avalonia.Controls;
+using Avalonia.Interactivity;
 using Avalonia.Markup.Xaml;
+using ProxyChecker.Dialogs.ViewModels;
 
 namespace ProxyChecker.Dialogs.Views;
 
@@ -8,6 +10,8 @@ public partial class UpdateDialog : UserControl
     public UpdateDialog()
     {
         InitializeComponent();
+        Loaded += (s, e) => UpdateViewModel.IsUpdateDialogOpen = true;
+        Unloaded += (s, e) => UpdateViewModel.IsUpdateDialogOpen = false;
     }
 
     private void InitializeComponent()

Services/UpdateService.cs

@@ -11,6 +11,7 @@ public class UpdateService
     private const string RepoUrl = "https://github.com/interface95/ProxyChecker";
     private UpdateManager? _updateManager;
     private UpdateInfo? _updateInfo;
+    private Task<UpdateInfo?>? _checkUpdateTask;
 
     public bool IsSupported => true;
 
@@ -21,7 +22,18 @@ public async Task InitializeAsync()
         _updateManager = new UpdateManager(source);
     }
 
-    public async Task<UpdateInfo?> CheckForUpdatesAsync()
+    public Task<UpdateInfo?> CheckForUpdatesAsync()
+    {
+        if (_checkUpdateTask != null && !_checkUpdateTask.IsCompleted)
+        {
+            return _checkUpdateTask;
+        }
+
+        _checkUpdateTask = CheckForUpdatesInternalAsync();
+        return _checkUpdateTask;
+    }
+
+    private async Task<UpdateInfo?> CheckForUpdatesInternalAsync()
     {
         if (_updateManager == null) await InitializeAsync();