{"record":{"id":"c42daf4d04b13ab2","repo":"MahApps/MahApps.Metro","slug":"the-light-flyout-theme-only-works-if-the-window-th","errorCode":null,"errorMessage":"The Light Flyout theme only works if the window theme abides the naming convention. See ThemeManager.GetInverseAppTheme for more infos","messagePattern":"The Light Flyout theme only works if the window theme abides the naming convention\\. See ThemeManager\\.GetInverseAppTheme for more infos","errorType":"exception","errorClass":"InvalidOperationException","httpStatus":null,"severity":"error","filePath":"src/MahApps.Metro/Controls/Flyout.cs","lineNumber":714,"sourceCode":"                    ThemeManager.Current.ApplyThemeResourcesFromTheme(this.Resources, inverseTheme);\n                    break;\n\n                case FlyoutTheme.Dark:\n                    var darkTheme = windowTheme.BaseColorScheme == ThemeManager.BaseColorDark ? windowTheme : ThemeManager.Current.GetInverseTheme(windowTheme);\n                    if (darkTheme is null)\n                    {\n                        throw new InvalidOperationException(\"The Dark Flyout theme only works if the window theme abides the naming convention. \" +\n                                                            \"See ThemeManager.GetInverseAppTheme for more infos\");\n                    }\n\n                    ThemeManager.Current.ApplyThemeResourcesFromTheme(this.Resources, darkTheme);\n                    break;\n\n                case FlyoutTheme.Light:\n                    var lightTheme = windowTheme.BaseColorScheme == ThemeManager.BaseColorLight ? windowTheme : ThemeManager.Current.GetInverseTheme(windowTheme);\n                    if (lightTheme is null)\n                    {\n                        throw new InvalidOperationException(\"The Light Flyout theme only works if the window theme abides the naming convention. \" +\n                                                            \"See ThemeManager.GetInverseAppTheme for more infos\");\n                    }\n\n                    ThemeManager.Current.ApplyThemeResourcesFromTheme(this.Resources, lightTheme);\n                    break;\n            }\n        }\n\n        private void UpdateOpacityChange()\n        {\n            if (this.flyoutRoot is null || this.fadeOutFrame is null || System.ComponentModel.DesignerProperties.GetIsInDesignMode(this))\n            {\n                return;\n            }\n\n            if (!this.AnimateOpacity)\n            {\n                this.fadeOutFrame.Value = 1;","sourceCodeStart":696,"sourceCodeEnd":732,"githubUrl":"https://github.com/MahApps/MahApps.Metro/blob/72099e310bac2d12ac98fd7560b69679252519f5/src/MahApps.Metro/Controls/Flyout.cs#L696-L732","documentation":"Thrown by Flyout.ChangeFlyoutTheme when Theme==FlyoutTheme.Light and the needed light theme cannot be resolved. If the window theme's BaseColorScheme is already Light, the window theme is used directly; otherwise GetInverseTheme is called and returns null when the window theme name doesn't follow the Light/Dark naming convention.","triggerScenarios":"Setting Flyout.Theme=Light on a dark-themed window whose custom theme name lacks the Light/Dark convention; the light inverse variant was never registered.","commonSituations":"Custom dark theme registered without a light counterpart; non-conventional theme naming; incomplete theme resource pack.","solutions":["Register a light counterpart theme following the naming convention.","Use Flyout.Theme=Adapt to inherit the window theme without needing an inverse.","Use built-in MahApps themes which provide both variants.","Pre-check ThemeManager.Current.GetInverseTheme and fall back if null."],"exampleFix":null,"handlingStrategy":"validation","validationCode":"var windowTheme = ThemeManager.Current.DetectTheme(window);\nFlyoutTheme desired = FlyoutTheme.Light;\n\nif (windowTheme is not null\n    && windowTheme.BaseColorScheme != ThemeManager.BaseColorLight\n    && ThemeManager.Current.GetInverseTheme(windowTheme) is null)\n{\n    desired = FlyoutTheme.Adapt; // no light counterpart available\n}\nflyout.Theme = desired;","typeGuard":null,"tryCatchPattern":"try { flyout.Theme = FlyoutTheme.Light; }\ncatch (InvalidOperationException ex) when (ex.Message.Contains(\"Light Flyout theme\"))\n{\n    flyout.Theme = FlyoutTheme.Adapt;\n}","preventionTips":["Register a light counterpart theme following the naming convention.","Pre-check GetInverseTheme for light resolution.","Fall back to Adapt when no light variant exists."],"tags":["wpf","theming","mahapps","flyout","configuration"],"backgroundTag":null,"analyzedSha":"72099e310bac2d12ac98fd7560b69679252519f5","analyzedAt":"2026-08-13T20:19:34.419Z","schemaVersion":2},"datasetVersion":"2026-08-14T00:17:13.853Z"}