Getting error using RadComboBox control

[Jon]

This is in a Maui Embedded Project.  Other Telerik Controls are working. 

Xaml:

<telerik:RadComboBox AutomationId="staticItemsComboBox">
    <telerik:RadComboBox.ItemsSource>
        <x:Array Type="{x:Type x:String}">
            <x:String>USA</x:String>
            <x:String>Uganda</x:String>
            <x:String>Ukraine</x:String>
            <x:String>Canada</x:String>
            <x:String>France</x:String>
            <x:String>Italy</x:String>
            <x:String>United Kingdom</x:String>
            <x:String>China</x:String>
            <x:String>Japan</x:String>
        </x:Array>
    </telerik:RadComboBox.ItemsSource>
</telerik:RadComboBox>

StackTrace:

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
 ---> System.TypeInitializationException: The type initializer for 'Telerik.Maui.Controls.RadComboBox' threw an exception.
 ---> System.TypeInitializationException: The type initializer for 'Telerik.Maui.Controls.ComboBoxConstants' threw an exception.
 ---> System.NullReferenceException: Object reference not set to an instance of an object.
   at Telerik.Maui.Controls.ComboBoxConstants..cctor()
   --- End of inner exception stack trace ---
   at Telerik.Maui.Controls.RadComboBox..cctor()
   --- End of inner exception stack trace ---
   at System.Reflection.ConstructorInvoker.InterpretedInvoke(Object obj, Span`1 args, BindingFlags invokeAttr)
   --- End of inner exception stack trace ---
   at System.RuntimeType.CreateInstanceMono(Boolean nonPublic, Boolean wrapExceptions)
   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean wrapExceptions)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic, Boolean wrapExceptions)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic)
   at System.Activator.CreateInstance(Type type)
   at Microsoft.Maui.Controls.Xaml.CreateValuesVisitor.Visit(ElementNode node, INode parentNode) in D:\a\_work\1\s\src\Controls\src\Xaml\CreateValuesVisitor.cs:line 102
   at Microsoft.Maui.Controls.Xaml.ElementNode.Accept(IXamlNodeVisitor visitor, INode parentNode) in D:\a\_work\1\s\src\Controls\src\Xaml\XamlNode.cs:line 159
   at Microsoft.Maui.Controls.Xaml.ElementNode.Accept(IXamlNodeVisitor visitor, INode parentNode) in D:\a\_work\1\s\src\Controls\src\Xaml\XamlNode.cs:line 155
   at Microsoft.Maui.Controls.Xaml.ElementNode.Accept(IXamlNodeVisitor visitor, INode parentNode) in D:\a\_work\1\s\src\Controls\src\Xaml\XamlNode.cs:line 155
   at Microsoft.Maui.Controls.Xaml.RootNode.Accept(IXamlNodeVisitor visitor, INode parentNode) in D:\a\_work\1\s\src\Controls\src\Xaml\XamlNode.cs:line 212
   at Microsoft.Maui.Controls.Xaml.XamlLoader.Visit(RootNode rootnode, HydrationContext visitorContext, Boolean useDesignProperties) in D:\a\_work\1\s\src\Controls\src\Xaml\XamlLoader.cs:line 207
   at Microsoft.Maui.Controls.Xaml.XamlLoader.Load(Object view, String xaml, Assembly rootAssembly, Boolean useDesignProperties) in D:\a\_work\1\s\src\Controls\src\Xaml\XamlLoader.cs:line 78
   at Microsoft.Maui.Controls.Xaml.XamlLoader.Load(Object view, String xaml, Boolean useDesignProperties) in D:\a\_work\1\s\src\Controls\src\Xaml\XamlLoader.cs:line 53
   at Microsoft.Maui.Controls.Xaml.XamlLoader.Load(Object view, Type callingType) in D:\a\_work\1\s\src\Controls\src\Xaml\XamlLoader.cs:line 49
   at Microsoft.Maui.Controls.Xaml.Extensions.LoadFromXaml[StopList](StopList view, Type callingType) in D:\a\_work\1\s\src\Controls\src\Xaml\ViewExtensions.cs:line 37
   at TransportACE_Maui.Source.UI.StopList.InitializeComponent() in C:\apacheta_git\TransportACE_HME\TransportACE_Maui\Microsoft.Maui.Controls.SourceGen\Microsoft.Maui.Controls.SourceGen.CodeBehindGenerator\Source_Views_StopList.xaml.sg.cs:line 26
   at TransportACE_Maui.Source.UI.StopList..ctor(StopListViewModel viewModel) in C:\apacheta_git\TransportACE_HME\TransportACE_Maui\Source\Views\StopList.xaml.cs:line 13
   at System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2[[Microsoft.Extensions.DependencyInjection.ServiceLookup.RuntimeResolverContext, Microsoft.Extensions.DependencyInjection, Version=7.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60],[System.Object, System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].VisitCallSiteMain(ServiceCallSite callSite, RuntimeResolverContext argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitDisposeCache(ServiceCallSite transientCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2[[Microsoft.Extensions.DependencyInjection.ServiceLookup.RuntimeResolverContext, Microsoft.Extensions.DependencyInjection, Version=7.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60],[System.Object, System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].VisitCallSite(ServiceCallSite callSite, RuntimeResolverContext argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve(ServiceCallSite callSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.RuntimeServiceProviderEngine.<>c__DisplayClass4_0.<RealizeService>b__0(ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(Type serviceType, ServiceProviderEngineScope serviceProviderEngineScope)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(Type serviceType)
   at Microsoft.Maui.MauiContext.WrappedServiceProvider.GetService(Type serviceType) in D:\a\_work\1\s\src\Core\src\MauiContext.cs:line 68
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetService[StopList](IServiceProvider provider)
   at TransportACE.Droid.StopsListMaui.OnCreate(Bundle bundle) in C:\apacheta_git\TransportACE_HME\TransportACE_Maui\Platforms\Android\Source\UITasks\StopsListMaui.cs:line 199

[Maria]

Hello Jon,

Thank you for the XAML snippet and provided stack trace.

I made a sample project with the code snippet you sent. I noticed that you have not set the x: Name to the ComboBox control. Can you please add this to your project and see if the exception is thrown again?

I am sending you a link to the issue which might occur if the x: Name is not set: Getting a XamlC error when trying to use common xmlns only in XAML without x:Name.

I tried to reproduce it but on my side, the code is buildable and works as expected once the x:Name property is set. I tested it with Visual Studio 2022, NET 7 version, and Telerik Ui for Maui 5.1.0 version. Can you please share more information what is the setup on your side? In addition, I am sending you the project I made. Can you please modify it if I have missed something on my side?

Looking forward to your answer.

 

[Jon]

I get the same error after adding x:Name 

[Maria]

Hello Jon, 

Please see the attached project in my previous reply. Could you please modify it so I can test the unwanted behavior on my side? With the current information, I can't reproduce the exception.

Looking forward to your reply.

[Jon]

Hi Maria.  I have a workaround now using the Maui Picker instead.  Have to finish up some other sprint work but once the sprint is over and I have time I will try to create a repro project for this issue and the other issue I reported with RadSegmentedControl. 

[Maria]

Hello Jon,

Do let us know once you manage to isolate the issue. I will be happy to assist you.

[Jon]

Here is the sample application.  Just run on an android device.  You can set a breakpoint in MainActivity.cs line 57 and you will see the exception: jdunaway/RadComboBoxSample: An Example of RadComboBox error in a MAUI Embedding application (github.com)

[Maria]

Hello Jon,

Thank you for the isolated project.

I reproduced the exception on my side. I have logged an item on your behalf in our public feedback portal. I am sending you a link to the item: Null Reference exception when using Native embedding. You can subscribe to the item to track its progress and get notified by email for any status changes. I have updated your Telerik points as well.

Let me know if I can assist you further.

Regards,
Maria
Progress Telerik

[Pushpalatha]

Still the issue exists. The Telerik MAUI Combobox does not bind the values. It throws exception. Please notify once the control works. Thanks.

[Didi]

Hi Pushpalatha,

The behavior happens when native embedding is used. We have this logged here: https://feedback.telerik.com/maui/1604076-null-reference-exception-when-using-native-embedding 
Press the follow button to track its progress. 

If you do not use native embedding approach the control works as expected.