{"record":{"id":"4cb7258ef94b66fa","repo":"PrismLibrary/Prism","slug":"no-registration-found-for-the-region-view-viewtype-fullname","errorCode":null,"errorMessage":"No registration found for the Region View '{viewType.FullName}'.","messagePattern":"No registration found for the Region View '(.+?)'\\.","errorType":"exception","errorClass":"KeyNotFoundException","httpStatus":null,"severity":"error","filePath":"src/Maui/Prism.Maui/Navigation/Regions/RegionViewRegistry.cs","lineNumber":57,"sourceCode":"            items.Add(getContentDelegate(container));\n        }\n\n        return items;\n    }\n\n    /// <summary>\n    /// Registers a content type with a region name.\n    /// </summary>\n    /// <param name=\"regionName\">Region name to which the <paramref name=\"viewType\"/> will be registered.</param>\n    /// <param name=\"viewType\">Content type to be registered for the <paramref name=\"regionName\"/>.</param>\n    public void RegisterViewWithRegion(string regionName, Type viewType)\n    {\n        RegisterViewWithRegion(regionName, c =>\n        {\n            var registry = c.Resolve<IRegionNavigationRegistry>();\n            var registration = registry.Registrations.FirstOrDefault(x => x.Type == ViewType.Region && x.View == viewType);\n            if (registration is null)\n                throw new KeyNotFoundException($\"No registration found for the Region View '{viewType.FullName}'.\");\n\n            return registry.CreateView(c, registration.Name);\n        });\n    }\n\n    /// <summary>\n    /// Registers a content type with a region name.\n    /// </summary>\n    /// <param name=\"regionName\">Region name to which the <paramref name=\"targetName\"/> will be registered.</param>\n    /// <param name=\"targetName\">Content type to be registered for the <paramref name=\"regionName\"/>.</param>\n    public void RegisterViewWithRegion(string regionName, string targetName)\n    {\n        RegisterViewWithRegion(regionName, c =>\n        {\n            var registry = c.Resolve<IRegionNavigationRegistry>();\n            return registry.CreateView(c, targetName);\n        });\n    }","sourceCodeStart":39,"sourceCodeEnd":75,"githubUrl":"https://github.com/PrismLibrary/Prism/blob/358118cd640d9a22ff8cf21c8ad197fa038b7990/src/Maui/Prism.Maui/Navigation/Regions/RegionViewRegistry.cs#L39-L75","documentation":"RegionViewRegistry.RegisterViewWithRegion(Type) resolves a factory that looks up the view type in IRegionNavigationRegistry.Registrations; if no Region-type registration matches the viewType, a KeyNotFoundException with the view's full name is thrown. The view must first be registered (via ViewType.Region registration) before the region registry can create it.","triggerScenarios":"Calling containerProvider.Resolve ... or regionViewRegistry.RegisterViewWithRegion(regionName, typeof(SomeView)) when SomeView was never registered in the DI/region registry (missing navigation registration, e.g. never registered via RegisterForNavigation with Region view type).","commonSituations":"Forgetting a RegisterForNavigation/registration call during App.RegisterTypes or App.CreateWindow; renaming/moving the view class so the stored registration's Type no longer matches; assembly scanning not including the view's assembly.","solutions":["Register the view: navigationBuilder.RegisterView<TView>(...) / RegisterForNavigation<TView>() so a Region-type registration exists.","Verify the exact Type passed to RegisterViewWithRegion matches the registered type (same assembly and full name).","Check that the assembly containing the view is scanned/loaded; ensure IRegionNavigationRegistry contains the expected entry."],"exampleFix":"// before\ncontainerRegistry.RegisterViewWithRegion(\"MainRegion\", typeof(UndefinedView)); // never registered\n// after\ncontainerRegistry.RegisterForNavigation<MainView>(\"MainView\");\ncontainerRegistry.RegisterViewWithRegion(\"MainRegion\", typeof(MainView));","handlingStrategy":"try-catch","validationCode":"var registered = container.Resolve<IRegionNavigationRegistry>()\n    .Registrations.Any(x => x.Type == ViewType.Region && x.View == viewType);\nif (!registered)\n    throw new InvalidOperationException($\"{viewType.FullName} is not registered as a region view\");","typeGuard":"bool IsRegisteredRegionView(IRegionNavigationRegistry reg, Type t) =>\n    reg.Registrations.Any(x => x.Type == ViewType.Region && x.View == t);","tryCatchPattern":"try { registry.RegisterViewWithRegion(regionName, viewType); }\ncatch (KeyNotFoundException ex) { Console.WriteLine($\"Missing registration: {ex.Message}\"); }","preventionTips":["Always call RegisterForNavigation/RegisterView before RegisterViewWithRegion(Type)","Verify the Type matches the registered one after refactors","Confirm view assemblies are included in registration scanning"],"tags":["prism","regions","registration-missing","keynotfound"],"backgroundTag":"record-not-found","analyzedSha":"358118cd640d9a22ff8cf21c8ad197fa038b7990","analyzedAt":"2026-09-15T15:00:31.079Z","contentChangedAt":"2026-09-15T15:00:31.079Z","schemaVersion":2},"datasetVersion":"2026-09-16T04:17:20.429Z"}