{"record":{"id":"b4e426718cedab7f","repo":"PrismLibrary/Prism","slug":"the-iregionadapter-for-the-type-0-is-not-registered-in-the","errorCode":null,"errorMessage":"The IRegionAdapter for the type {0} is not registered in the region adapter mappings. You can register an IRegionAdapter for this control by overriding the ConfigureRegionAdapterMappings method in the bootstrapper.","messagePattern":"The IRegionAdapter for the type (.+?) is not registered in the region adapter mappings\\. You can register an IRegionAdapter for this control by overriding the ConfigureRegionAdapterMappings method in the bootstrapper\\.","errorType":"exception","errorClass":"KeyNotFoundException","httpStatus":null,"severity":"error","filePath":"src/Maui/Prism.Maui/Navigation/Regions/Adapters/RegionAdapterMappings.cs","lineNumber":83,"sourceCode":"    /// <returns>The <see cref=\"IRegionAdapter\"/> mapped to the <paramref name=\"controlType\"/>.</returns>\n    /// <remarks>This class will look for a registered type for <paramref name=\"controlType\"/> and if there is not any,\n    /// it will look for a registered type for any of its ancestors in the class hierarchy.\n    /// If there is no registered type for <paramref name=\"controlType\"/> or any of its ancestors,\n    /// an exception will be thrown.</remarks>\n    /// <exception cref=\"KeyNotFoundException\">When there is no registered type for <paramref name=\"controlType\"/> or any of its ancestors.</exception>\n    public IRegionAdapter GetMapping(Type controlType)\n    {\n        Type currentType = controlType;\n\n        while (currentType != null)\n        {\n            if (mappings.TryGetValue(currentType, out IRegionAdapter value))\n            {\n                return value;\n            }\n            currentType = currentType.BaseType;\n        }\n        throw new KeyNotFoundException(string.Format(CultureInfo.CurrentCulture, Resources.NoRegionAdapterException, controlType));\n    }\n\n    /// <summary>\n    /// Returns the adapter associated with the type provided.\n    /// </summary>\n    /// <typeparam name=\"T\">The control type used to obtain the <see cref=\"IRegionAdapter\"/> mapped.</typeparam>\n    /// <returns>The <see cref=\"IRegionAdapter\"/> mapped to the <typeparamref name=\"T\"/>.</returns>\n    /// <remarks>This class will look for a registered type for <typeparamref name=\"T\"/> and if there is not any,\n    /// it will look for a registered type for any of its ancestors in the class hierarchy.\n    /// If there is no registered type for <typeparamref name=\"T\"/> or any of its ancestors,\n    /// an exception will be thrown.</remarks>\n    /// <exception cref=\"KeyNotFoundException\">When there is no registered type for <typeparamref name=\"T\"/> or any of its ancestors.</exception>\n    public IRegionAdapter GetMapping<T>()\n    {\n        return GetMapping(typeof(T));\n    }\n}\n","sourceCodeStart":65,"sourceCodeEnd":101,"githubUrl":"https://github.com/PrismLibrary/Prism/blob/358118cd640d9a22ff8cf21c8ad197fa038b7990/src/Maui/Prism.Maui/Navigation/Regions/Adapters/RegionAdapterMappings.cs#L65-L101","documentation":"RegionAdapterMappings.GetMapping walks the control type hierarchy looking for a registered IRegionAdapter and throws KeyNotFoundException (Resources.NoRegionAdapterException) when neither the type nor any base type has a mapping. Prism cannot adapt a region on a control it has no adapter for.","triggerScenarios":"Marking a control (e.g. a custom ContentView subclass or a third-party control) with RegionManager.RegionName when no adapter is registered for that type or its ancestors; calling GetMapping directly for an unmapped type.","commonSituations":"Using a third-party or custom control as a region without registering a custom IRegionAdapter; forgetting to override ConfigureRegionAdapterMappings; MAUI upgrades introducing a new control type Prism does not map by default.","solutions":["Override ConfigureRegionAdapterMappings in your PrismApp and register an adapter for the control type (or one of its base types)","Write a custom IRegionAdapter for the third-party/custom control and register it via RegisterMapping<TControl, TAdapter>","Host the control's region inside a mapped container (e.g. put region content in a ContentPresenter/ScrollView that Prism maps)","Verify the control type you registered matches the actual runtime type of the control"],"exampleFix":"// before\n// MyCustomControl used with RegionManager.RegionName, no adapter\n\n// after\nprotected override void ConfigureRegionAdapterMappings(IRegionAdapterMappings regionAdapterMappings)\n{\n    base.ConfigureRegionAdapterMappings(regionAdapterMappings);\n    regionAdapterMappings.RegisterMapping<MyCustomControl, MyCustomControlRegionAdapter>();\n}","handlingStrategy":"validation","validationCode":"bool mapped = mappings is not null; // no public lookup; instead ensure registration in ConfigureRegionAdapterMappings\n// Recommended: register before any view with RegionManager.RegionName loads","typeGuard":null,"tryCatchPattern":"try { var adapter = mappings.GetMapping(control.GetType()); }\ncatch (KeyNotFoundException) { /* no adapter for this control type — register one */ }","preventionTips":["Register an adapter for every custom/third-party control used as a region","Override ConfigureRegionAdapterMappings in your PrismApp for unmapped types","Prefer hosting regions in controls Prism maps by default (ContentPresenter, ScrollView, Layout)"],"tags":["prism","maui","regions","missing-registration"],"backgroundTag":"missing-dependency","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"}