{"record":{"id":"d87018205cf07271","repo":"PrismLibrary/Prism","slug":"argumentnullexception-for-regiontarget","errorCode":null,"errorMessage":"ArgumentNullException for 'regionTarget'","messagePattern":"ArgumentNullException for 'regionTarget'","errorType":"exception","errorClass":"ArgumentNullException","httpStatus":null,"severity":"error","filePath":"src/Maui/Prism.Maui/Navigation/Regions/Xaml/RegionManager.cs","lineNumber":90,"sourceCode":"    /// <summary>\n    /// Gets the value of the <see cref=\"DefaultViewProperty\"/> attached property for the specified region target.\n    /// </summary>\n    /// <param name=\"regionTarget\">The <see cref=\"VisualElement\"/> that hosts the default view.</param>\n    /// <returns>\n    /// The default view associated with the region. This can be a view name, a type, or an instance of the view.\n    /// </returns>\n    public static object GetDefaultView(VisualElement regionTarget) =>\n        regionTarget.GetValue(DefaultViewProperty);\n\n    /// <summary>\n    /// Sets the <see cref=\"RegionNameProperty\"/> attached property.\n    /// </summary>\n    /// <param name=\"regionTarget\">The object to adapt. This is typically a container (i.e a control).</param>\n    /// <param name=\"regionName\">The name of the region to register.</param>\n    public static void SetRegionName(VisualElement regionTarget, string regionName)\n    {\n        if (regionTarget == null)\n            throw new ArgumentNullException(nameof(regionTarget));\n\n        regionTarget.SetValue(RegionNameProperty, regionName);\n    }\n\n    /// <summary>\n    /// Gets the value for the <see cref=\"RegionNameProperty\"/> attached property.\n    /// </summary>\n    /// <param name=\"regionTarget\">The object to adapt. This is typically a container (i.e a control).</param>\n    /// <returns>The name of the region that should be created when\n    /// <see cref=\"RegionManagerProperty\"/> is also set in this element.</returns>\n    public static string GetRegionName(VisualElement regionTarget)\n    {\n        if (regionTarget == null)\n            throw new ArgumentNullException(nameof(regionTarget));\n\n        return regionTarget.GetValue(RegionNameProperty) as string;\n    }\n","sourceCodeStart":72,"sourceCodeEnd":108,"githubUrl":"https://github.com/PrismLibrary/Prism/blob/358118cd640d9a22ff8cf21c8ad197fa038b7990/src/Maui/Prism.Maui/Navigation/Regions/Xaml/RegionManager.cs#L72-L108","documentation":"RegionManager.SetRegionName sets the RegionName attached property on a VisualElement so a region can be created for it. The library throws ArgumentNullException because there is no meaningful target element to attach a region name to when the argument is null.","triggerScenarios":"Calling RegionManager.SetRegionName(null, \"SomeRegion\") — passing a null VisualElement as regionTarget.","commonSituations":"Programmatically wiring regions before a control is instantiated; a data-bound or factory-returned element that is null; refactoring where the element variable was removed.","solutions":["Pass the actual VisualElement (container control) you want the region attached to.","Guard against null element references (e.g. from FindByName or binding results) before calling.","Prefer XAML RegionName attached-property usage, which guarantees a live element."],"exampleFix":"// before\nRegionManager.SetRegionName(null, \"MainRegion\");\n// after\nif (myContainer != null)\n    RegionManager.SetRegionName(myContainer, \"MainRegion\");","handlingStrategy":"validation","validationCode":"if (regionTarget is null) throw new InvalidOperationException(\"Region target element must be created before SetRegionName\");","typeGuard":"if (regionTarget is VisualElement element && !string.IsNullOrWhiteSpace(regionName)) RegionManager.SetRegionName(element, regionName);","tryCatchPattern":"try { RegionManager.SetRegionName(target, name); }\ncatch (ArgumentNullException) { logger.LogWarning(\"Skipped SetRegionName: null target\"); }","preventionTips":["Prefer XAML RegionName attached property over programmatic assignment.","Null-check elements from FindByName/factory calls before use.","Run region wiring after the visual tree is loaded."],"tags":["prism","maui","regions","argument-null","attached-property"],"backgroundTag":"null-argument","analyzedSha":"358118cd640d9a22ff8cf21c8ad197fa038b7990","analyzedAt":"2026-09-15T15:00:31.079Z","contentChangedAt":"2026-09-15T15:00:31.079Z","schemaVersion":2},"datasetVersion":"2026-09-23T08:17:48.524Z"}