HandyOrg/HandyControl · error · ArgumentNullException

不能为 null

Error message

{nameof(window)} 不能为 null

What it means

Validation guard at the entry of StartFullScreen: the window argument is null. The helper stores and mutates window state (styles, DWM transitions, monitor metrics) via Win32 interop, so a null reference must be rejected before any DependencyProperty or handle access. The message string is built with nameof(window) — 'window 不能为 null' means 'window cannot be null'.

Solutions

  1. Pass a live, initialized Window instance to StartFullScreen/EndFullScreen — construct the window and ensure it is loaded before going full screen
  2. Guard at the call site: 'if (window == null) return;' or log and skip when the window reference may be missing (e.g. during shutdown)
  3. For APIs that can legitimately receive null, make the parameter nullable and treat null as a no-op instead of throwing
Defensive patterns

Strategy: validation

When it happens

Trigger: Thrown at src/Shared/HandyControl_Shared/Tools/Helper/FullScreenHelper.cs:41 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of HandyOrg/HandyControl@2c0875ebd6 (2026-09-14). Data as JSON: /api/errors/076707a1c38421f7. Report an issue: GitHub.

Appendix: source

Thrown at src/Shared/HandyControl_Shared/Tools/Helper/FullScreenHelper.cs:41

    /// <summary>
    /// 用于记录窗口全屏前样式的附加属性
    /// </summary>
    private static readonly DependencyProperty BeforeFullScreenWindowStyleProperty =
        DependencyProperty.RegisterAttached("BeforeFullScreenWindowStyle",
            typeof(InteropValues.WindowStyles?), typeof(FullScreenHelper));

    /// <summary>
    /// 开始进入全屏模式
    /// 进入全屏模式后，窗口可通过 API 方式（也可以用 Win + Shift + Left/Right）移动，调整大小，但会根据目标矩形寻找显示器重新调整到全屏状态。
    /// 进入全屏后，不要修改样式等窗口属性，在退出时，会恢复到进入前的状态
    /// 进入全屏模式后会禁用 DWM 过渡动画
    /// </summary>
    public static void StartFullScreen(System.Windows.Window window)
    {
        if (window == null)
        {
            throw new ArgumentNullException(nameof(window), $"{nameof(window)} 不能为 null");
        }

        //确保不在全屏模式
        if (window.GetValue(BeforeFullScreenWindowPlacementProperty) == null &&
            window.GetValue(BeforeFullScreenWindowStyleProperty) == null)
        {
            var hwnd = new WindowInteropHelper(window).EnsureHandle();
            var hwndSource = HwndSource.FromHwnd(hwnd);

            //获取当前窗口的位置大小状态并保存
            var placement = InteropMethods.GetWindowPlacement(hwnd);
            window.SetValue(BeforeFullScreenWindowPlacementProperty, placement);

            //修改窗口样式
            var style = (InteropValues.WindowStyles) InteropMethods.GetWindowLongPtr(hwnd, InteropValues.GWL_STYLE);
            window.SetValue(BeforeFullScreenWindowStyleProperty, style);
            //将窗口恢复到还原模式，在有标题栏的情况下最大化模式下无法全屏,
            //这里采用还原，不修改标题栏的方式

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