Troubleshooting known issues

Article
05/14/2024

This article describes some of the known issues with .NET Multi-platform App UI (.NET MAUI), and how you can solve or work around them. The .NET MAUI repository also details some known issues.

Can't locate the .NET MAUI workloads

There are two options for installing the .NET MAUI workloads:

Visual Studio on Windows can install .msi files for each workload pack.
dotnet workload install commands.

On Windows, if you run a dotnet workload install after installing .NET MAUI through the Visual Studio installer, Visual Studio can enter a state where it can't locate the .NET MAUI workloads. You'll receive build errors telling you to install the .NET MAUI workloads, and it's possible to enter a state where the workloads can't be repaired or reinstalled. For more information, see the GitHub issue dotnet/sdk#22388.

Windows

The solution to this issue on Windows is to uninstall the .NET MAUI workloads through the CLI, uninstall any .NET SDKs in Control Panel, and uninstall the .NET MAUI workloads in Visual Studio. These uninstalls can be accomplished with the following process:

Run dotnet workload uninstall maui if you ever used the dotnet workload install commands.
Uninstall any standalone .NET SDK installers from Control Panel. These installers have names similar to Microsoft .NET SDK 6.0.300.
In every instance of Visual Studio, uninstall the .NET Multi-platform App UI development, and .NET desktop development Visual Studio workloads.

Then, check if there are additional .msi files that need to be uninstalled by running the following command:

reg query HKLM\SOFTWARE\Microsoft\Windows\currentversion\uninstall\ -s -f manifest

This reg query command lists .NET 6+ SDKs that are still installed on your machine, such as:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\currentversion\uninstall\{EEC1BB5F-3391-43C2-810E-42D78ADF3140}
    InstallSource    REG_SZ    C:\ProgramData\Microsoft\VisualStudio\Packages\Microsoft.MacCatalyst.Manifest-6.0.300,version=125.179.40883,chip=x64,productarch=neutral\
    DisplayName    REG_SZ    Microsoft.NET.Sdk.MacCatalyst.Manifest-6.0.300

If you receive similar output, you should copy the GUID for each package and uninstall the package with the msiexec command:

msiexec /x {EEC1BB5F-3391-43C2-810E-42D78ADF3140} /q IGNOREDEPENDENCIES=ALL

Then, you should keep executing the reg query command until it doesn't return any results. Once there are no more results and all .NET 6+ SDKs are uninstalled, you should also consider deleting the following folders:

C:\Program Files\dotnet\sdk-manifests
C:\Program Files\dotnet\metadata
C:\Program Files\dotnet\packs
C:\Program Files\dotnet\library-packs
C:\Program Files\dotnet\template-packs
C:\Program Files\dotnet\sdk\6.* or C:\Program Files\dotnet\sdk\7.*
C:\Program Files\dotnet\host\fxr\6.* or C:\Program Files\dotnet\host\fxr\7.*

After following this process, you should be able to reinstall .NET MAUI either through Visual Studio, or by installing your chosen .NET SDK version and running the dotnet workload install maui command.

Mac

Visual Studio for Mac's installer and updater uses dotnet workload install commands to install the .NET MAUI .pkg files.

Since .pkg files can't be uninstalled, the simplest approach to uninstalling the workloads on a Mac is to run the following commands to delete the specified folders:

rm -r ~/.dotnet/
sudo rm -r /usr/local/share/dotnet/

After executing these commands, you should be able to reinstall .NET MAUI either through Visual Studio for Mac, or by installing your chosen .NET SDK version and running dotnet workload install maui command.

Platform version isn't present

Visual Studio may not be resolving the required workloads if you try to compile a project and receive an error similar to the following text:

Platform version is not present for one or more target frameworks, even though they have specified a platform: net8.0-android, net8.0-ios, net8.0-maccatalyst

This problem typically results from having an x86 and x64 SDK installed, and the x86 version is being used. Visual Studio and .NET MAUI require the x64 .NET SDK. If your operating system has a system-wide PATH variable that is resolving the x86 SDK first, you need to fix that by either removing the x86 .NET SDK from the PATH variable, or promoting the x64 .NET SDK so that it resolves first. For more information on troubleshooting x86 vs x64 SDK resolution, see Install .NET on Windows - Troubleshooting.

Type or namespace 'Default' doesn't exist

When using the Contacts API, you may see the following error related to iOS and macOS:

The type or namespace name 'Default' does not exist in the namespace 'Contacts' (are you missing an assembly reference?)

The iOS and macOS platforms contain a root namespace named Contacts. This conflict causes a conflict for those platforms with the Microsoft.Maui.ApplicationModel.Communication namespace, which contains a Contacts type. The Microsoft.Maui.ApplicationModel.Communication namespace is automatically imported by the <ImplicitUsings> setting in the project file.

To write code that also compiles for iOS and macOS, fully qualify the Contacts type. Alternatively, provide a using directive at the top of the code file to map the Communication namespace:

using Communication = Microsoft.Maui.ApplicationModel.Communication;

// Code that uses the namespace:
var contact = await Communication.Contacts.Default.PickContactAsync();

Xcode isn't currently installed or couldn't be found

After you install the Xcode command line tools using xcode-select --install, Visual Studio for Mac might show a "Xcode is not currently installed or could not be found" message when you attempt to build .NET MAUI apps that target iOS or Mac Catalyst. In this scenario, check that you also have Xcode installed from the App Store. Then, launch Xcode and go to Xcode > Preferences > Locations > Command Line Tools and check if the drop-down is empty. If it's empty, select the drop-down, and then select the location of the Xcode command line tools. Then close Xcode and restart Visual Studio for Mac.

Couldn't find a valid Xcode app bundle

If you receive the error "Could not find a valid Xcode app bundle at '/Library/Developer/CommandLineTools'" when you attempt to build .NET MAUI apps that target iOS or Mac Catalyst, try the solution described in Xcode isn't currently installed or couldn't be found. If you're still unable to access the Xcode > Preferences > Locations > Command Line Tools drop-down, run the following command:

sudo xcode-select --reset

Xcode version can't be located

In some scenarios, building a .NET MAUI app on iOS or Mac Catalyst may attempt to use a version of Xcode that's no longer installed on your machine. When this occurs you'll receive an error message similar to:

xcodebuild: error: SDK "/Applications/Xcode_14.1.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk" cannot be located.
xcrun: error: sh -c '/Applications/Xcode_14.1.app/Contents/Developer/usr/bin/xcodebuild -sdk /Applications/Xcode_14.1.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk -find dsymutil 2> /dev/null' failed with exit code 16384: (null) (errno=Invalid argument)
xcrun: error: unable to find utility "dsymutil", not a developer tool or in PATH

When building an app, .NET for iOS and .NET for Mac Catalyst use the following process to determine which version of Xcode to use:

If the MD_APPLE_SDK_ROOT environment variable is set, use its value.
If the ~/Library/Preferences/Xamarin/Settings.plist file exists, use the value defined inside it.
Use the value of xcode-select -p.
Use /Applications/Xcode.app.

Therefore, the recommended approach to specifying the location of Xcode on your machine is to set the MD_APPLE_SDK_ROOT environment variable to the path of the Xcode version. For more information, see Build with a specific version of Xcode.

You can then safely delete ~/Library/Preferences/Xamarin/Settings.plist from your machine.

Diagnose issues in Blazor Hybrid apps

BlazorWebView has built-in logging that can help you diagnose problems in your Blazor Hybrid app. There are two steps to enable this logging:

Enable BlazorWebView and related components to log diagnostic information.
Configure a logger to write the log output to where you can view it.

For more information, see Diagnosing issues in Blazor Hybrid apps.

Disable image packaging

For troubleshooting purposes, image resource packaging can be disabled by setting the $(EnableMauiImageProcessing) build property to false in the first <PropertyGroup> node in your project file:

<EnableMauiImageProcessing>false</EnableMauiImageProcessing>

Disable splash screen packaging

For troubleshooting purposes, splash screen resource generation can be disabled by setting the $(EnableSplashScreenProcessing) build property to false in the first <PropertyGroup> node in your project file:

<EnableSplashScreenProcessing>false</EnableSplashScreenProcessing>

Disable font packaging

For troubleshooting purposes, font resource packaging can be disabled by setting the $(EnableMauiFontProcessing) build property to false in the first <PropertyGroup> node in your project file:

<EnableMauiFontProcessing>false</EnableMauiFontProcessing>

Disable asset file packaging

For troubleshooting purposes, asset file resource packaging can be disabled by setting the $(EnableMauiAssetProcessing) build property to false in the first <PropertyGroup> node in your project file:

<EnableMauiAssetProcessing>false</EnableMauiAssetProcessing>

Generate a blank splash screen

For troubleshooting purposes, a blank splash screen can be generated if you don't have a <MauiSplashScreen> item and you don't have a custom splash screen. This can be achieved by setting the $(EnableBlankMauiSplashScreen) build property to true in the first <PropertyGroup> node in your project file:

<EnableBlankMauiSplashScreen>true</EnableBlankMauiSplashScreen>

Generating a blank splash screen will override any custom splash screen and will cause app store rejection. However, it can be a useful approach in testing to ensure that your app UI is correct.

Duplicate image filename errors

You may encounter build errors about duplicate image filenames:

One or more duplicate file names were detected. All image output filenames must be unique.

This occurs for MauiIcon and MauiImage items because from .NET 8, .NET MAUI checks to ensure that there are no duplicate image resource filenames.

The error will occur when you have identical filenames in multiple folders, and in certain circumstances when you have identical filenames with different extensions in different folders. For example, the build error will occur for a PNG file at Resources/Images/PNG/dotnet_bot.png and an SVG file at Resources/Images/SVG/dotnet_bot.svg because SVG files are converted to PNG files at build time.

The error will also occur if you use the Include attribute on a MauiImage item to include all images in a folder, and then also include a specific image file:

<MauiImage Include="Resources\Images\*" />
<MauiImage Include="Resources\Images\dotnet_bot.svg" BaseSize="168,208" />

If you receive this build error it can be fixed by ensuring that your project file doesn't include duplicate images. To do this, change any MauiIcon or MauiImage that references a specific file to use the Update attribute instead of the Include attribute:

<MauiImage Include="Resources\Images\*" />
<MauiImage Update="Resources\Images\dotnet_bot.svg" BaseSize="168,208" />

For information about MSBuild item element attributes, see Item element (MSBuild): Attributes and elements.

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