Errors, symptoms and code search

Part of Migrating to Uno Platform 7.0. Use this page to jump straight from a build error, a symptom or a piece of your code to the section that explains it.

Build errors and warnings

Look up the code or message you got, then follow the link for the fix.

Code or message Cause Details
NU1202 A project still targets net9.0-* .NET 9 is no longer supported
NU1605 WinAppSdkVersion is pinned to 1.x Windows App SDK minimum
CS1705 on WinRT.Runtime WindowsSdkPackageVersion selects a projection older than .87 Windows SDK projection
MSB4100 A condition uses the removed IsMacCatalyst or IsIOSOrCatalyst Mac Catalyst is removed
CS0104 on ScrollViewer, ComboBox or ScrollContentPresenter using Uno.UI.Xaml.Controls; next to the WinUI namespace Uno.UI.Toolkit types
ThumbnailMode not found Windows.Storage.ThumbnailMode is removed Windows.Storage.ThumbnailMode
CS7036 on GetTemplateChild Control.GetTemplateChild is no longer public, so an extension method bound instead Control.GetTemplateChild
UNOB0017 Reference to Uno.WinUI.WebAssembly or Uno.WinUI.Runtime.WebAssembly Uno.WinUI.WebAssembly
UNOB0020 A multi-targeted library was built against 6.x Platform targeting
UNOB0022 The SingleProject property The Uno.Sdk is required
UNOB0023 A runtime-enabled package provided no runtime assembly Runtime identifier properties, Cross-runtime libraries
UNOB0024 UnoRuntimeIdentifier or a sibling property is set Runtime identifier properties
UNOB0025 Runtime-enabled packages without a runtime host Runtime identifier properties
UNOB0026 A referenced assembly was built for a native renderer Runtime identifier properties
UNOB0027 A removed file suffix such as *.Apple.cs Removed file suffixes
UNOB0028 UnoSplashScreenColor UnoSplashScreenColor removed
UNOB0029 An app head doesn't use the Uno.Sdk The Uno.Sdk is required
UNOB0030 A library lists SkiaRenderer Skia on libraries
UNOB0033 A leftover Platforms/MacCatalyst folder Mac Catalyst is removed
UNOB0034, WMC0001: Unknown type 'LottieVisualSource' Lottie XAML on a Windows target without CommunityToolkit.WinUI.Lottie Lottie
UNOB0035 UnoFeatures lists Prism Prism Uno Feature removed
UXAML0001 Binding an attached property whose owner type can't be found Attached property owners
UXAML0006 A clr-namespace: declaration clr-namespace: xmlns form
UXAML0007 A removed conditional XAML prefix such as skia: Removed XAML prefixes
Uno0001 A not-implemented API, which can fail builds that set TreatWarningsAsErrors Uno0001
Property 'AreDimensionsConstrained' does not exist Layout-constraint members are removed Layout-constraint optimization
XAML build failure on IsNativeStyle The attribute is no longer recognized Native-style declaration
XAML build failure on ControlsResourcesVersion The member is removed Fluent resource-version types

Failures at run time

Symptom Cause Details
No drawing backend could be resolved at startup A head without the Uno.Sdk implicit packages got Uno.WinUI.Composition.Skia only through a library Skia on libraries
FileNotFoundException from SkiaSharp.Views.Windows.GlobalStaticResources.Initialize() Explicit SkiaSharp.Views.Uno.WinUI reference SkiaSharp.Views.Uno.WinUI
Could not load type … from assembly 'Uno.UI' on an MRT Core type A library or assembly-qualified name still targets 6.x MRT Core
Failures in code from a multi-targeted library A stale net*-ios or net*-android asset built against 6.x is now deployed Platform targeting
(MyEnum)GetValue(...) throws Custom value-type dependency properties now default to null Custom value types default to null
XamlParseException from XamlReader.Load or Hot Reload A clr-namespace: declaration clr-namespace: xmlns form
Crash on launch on Android, where the app used to start degraded Startup failures now propagate Android head uses the host builder
Failure at run time after pinning SkiaSharp Managed and native SkiaSharp packages at different versions SkiaSharp 4 is the default

Changes the compiler won't catch

These build cleanly and only show up when you run the app.

What you notice Why Details
iOS or tvOS settings seem to have disappeared after updating Settings moved to a new store and aren't migrated for you Application settings
ItemClickCommand="{Binding}" or Command="{Binding}" on a list does nothing The XAML still compiles, but the property is gone ItemClickCommand
Markup under a skia: or not_skia: style prefix applies everywhere, or nowhere A removed prefix is treated as an ordinary namespace Removed XAML prefixes
#if __IOS__ or ios: code in a library runs for the first time Platform assets of a library are now deployed Platform targeting
A *.skia.cs file compiles on mobile and WebAssembly too The suffix now covers every target except WinAppSDK Platform targeting
Number and date formats don't follow PrimaryLanguageOverride until restart The setter no longer swaps the culture UseLegacyPrimaryLanguageOverride
The backdrop material is hidden Backgrounds are no longer made transparent for you SystemBackdrop
A custom ContentControl renders nothing A control with no template no longer bypasses the ContentPresenter ContentControl subclasses
A selected list item isn't scrolled into view Only a focused list brings a new selection into view List selection
A long press no longer clicks or selects A touch or pen hold is no longer a tap Holds
A drag or splitter lags the pointer slightly No ManipulationDelta right after ManipulationStarted Manipulation deltas
A page loses its state on Back Pages follow NavigationCacheMode, if the app set UseWinUIBehavior to false Frame.UseWinUIBehavior
Content draws under the Android status bar Apps are always edge-to-edge IsEdgeToEdgeEnabled
A popup no longer closes on outside tap, or content alignment changed A compatibility flag the app set is gone Compatibility flags, UseLegacyContentAlignment
An MSIX package installed outside the Microsoft Store fails to install or start Packaged heads depend on the Windows App Runtime instead of bundling it Packaged Windows heads
Suspending no longer fires on desktop Skia Desktop doesn't report suspension App lifecycle events
OnLaunched sees Launch for a URL or shortcut launch on iOS A cold-start activation arrives after OnLaunched Activation
A relative WebView2.Source or NavigateUri silently fails Relative URIs now compile to ms-resource:///Files/… Relative URIs
Fluent controls have no template They come only from XamlControlsResources Fluent styles
Letterbox bars are transparent, not black MediaPlayerElement no longer paints a backdrop MediaPlayerPresenter
Rendering differences or more memory on some GPUs Vulkan is the default on Android, Linux and Windows Vulkan
An Android drawable no longer resolves Retargeted drawables keep their file extension Retargeted drawables, ms-appx:/// lookups
A WebAssembly sign-in timeout looks different A timeout returns ErrorHttp instead of UserCancel WebAuthenticationBroker

Search your code

Each row is a literal string to search for across your C#, XAML and MSBuild files. Any match means that section applies to you, so this is the quickest way to scope an upgrade by hand or with an AI agent. The list covers the most common names rather than every change, so the compiler still has the last word.

Search for Go to
Uno.UI.Toolkit Uno.UI.Toolkit types
Runtime.Skia, MediaPlayer.Skia, WebView.Skia, SkiaHost, SkiaHostBuilder Runtime host renames
Microsoft.UI.Xaml.NativeApplication, Microsoft.UI.Xaml.ApplicationActivity, NativePage, AppBuilder Runtime host renames, Android head
Microsoft.Windows.ApplicationModel.Resources in a string, , Uno.UI", , Uno" MRT Core
OnActivated, unoprotocolactivation Activation
.Suspending, .Resuming, .EnteredBackground, .LeavingBackground, RequiresPointerMode App lifecycle events
LocalSettings, RoamingSettings, StandardUserDefaults Application settings
ContextHelper, GetBaseActivityEvents Android context APIs
FeatureConfiguration, PrimaryLanguageOverride Removed feature flags
Sdk="Microsoft.NET.Sdk" on an app head, SingleProject, uap10.0 The Uno.Sdk is required
net9.0 .NET 9 is no longer supported
maccatalyst, __MACCATALYST__, IsMacCatalyst, IsIOSOrCatalyst, MacCatalystProjectFolder Mac Catalyst is removed
SupportedOSPlatformVersion, TargetPlatformMinVersion Minimum OS versions
WindowsSdkPackageVersion Windows SDK projection
UnoDisableHotRestartHelperGeneration iOS Hot Restart
UnoSplashScreenColor UnoSplashScreenColor removed
UnoRuntimeIdentifier, UnoUIRuntimeIdentifier, UnoWinRTRuntimeIdentifier Runtime identifier properties
HAS_UNO_SKIA, __UNO_SKIA, UNO_REFERENCE_API Removed symbols, Symbols and project shape
skia:, netstdref:, androidskia:, iosskia:, macos:, not_mux:, xamarin:, legacy: Removed XAML prefixes
Files named *.Apple.cs, *.reference.cs, *.iOSmacOS.cs, *.skia.cs Removed file suffixes, Platform targeting
Prism, Lottie in UnoFeatures; Uno.WinUI.Lottie Prism, Lottie
SKXamlCanvas, SKSwapChainPanel, SkiaSharp.Views.Uno.WinUI SkiaSharp.Views.Uno.WinUI
SKPaint, SKCanvas, SkiaSharpVersion SkiaSharp 4 is the default
GLCanvasElement, CullFaceMode GLCanvasElement
UseVulkanOn, UseOpenGLOn, PreferGLESOverGLOnX11 Vulkan
ConfigureUniversalImageLoader, bundle:// Uno.UniversalImageLoader, bundle://
AdaptNative, HtmlId, HtmlElementAttribute, SetHtmlAttribute, RegisterHtmlEventHandler Native element hosting
BindableView, BindableUIView, Android.Views.View, UIKit.UIView Native base classes
NativeDefault, IsNativeStyle, UseNativePopup, AreDimensionsConstrained Native rendering types and helpers
IJSObject, InvokeJSWithInterop, TSInteropMessage WebAssembly interop
ItemClickCommand, and Command= on ListView or GridView ItemClickCommand
GetTemplateChild, VisualTreeHelper.GetChildren GetTemplateChild, GetChildren
WindowSizeChangedEventHandler, VisibilityChangedEventArgs Window events
Thickness.Empty, CornerRadius.None, Brush brush =, GridLength width = Implicit conversions
new StackPanel {, new Border {, new ScrollViewer { Collection initializers
IAnimatedVisualSource, LottieVisualSourceBase IAnimatedVisualSource
DependencyPropertyValuePrecedences DependencyPropertyValuePrecedences
IsLocalResource IsLocalResource is renamed
new Control(), new Panel(), new Timeline(), new DataTemplate(, FrameworkTemplateBuilder Constructor accessibility
is ContentControl, is TextBox, is Border Type-hierarchy changes
.Background on a FrameworkElement, TextBlock, Image or Shape; FrameworkElement.BackgroundProperty Background
ref thickness., Duration.Type, .GridUnitType =, GuidHelper.Equals, .LoadContent() WinRT projection alignment
clr-namespace:, legacy:ListView, legacy:GridView clr-namespace: xmlns form, legacy: lists
XamlDefault, XamlAppBar, DefaultFlyoutPresenter, BasedOn="{StaticResource Xaml XamlDefault* styles
themeresources_v2, XamlControlsResourcesV2, ControlsResourcesVersion Fluent theme resources, Resource-version types
SystemBackdrop SystemBackdrop
Resource.Drawable, FindResourceId Retargeted drawables
WithUnoHelpers, WebAuthenticationBroker Authentication on WebAssembly