After upgrading from Telerik UI for .NET MAUI 13.0.0 → 13.2.0, a NullReferenceException is thrown inside SchedulerAgendaView.Init() on Windows (WinUI3) whenever a RadScheduler with an AgendaViewDefinition is used. The scheduler never renders and the app receives an unhandled exception.

Steps to Reproduce:

1. Create a .NET MAUI app targeting Windows (WinUI3)
2. Add a ContentPage (or any page) with a RadScheduler in XAML, including at least one AgendaViewDefinition in ViewDefinitions:

<telerik:RadScheduler AppointmentsSource="{Binding Appointments}">
    <telerik:RadScheduler.ViewDefinitions>
        <telerik:AgendaViewDefinition />
        <telerik:DayViewDefinition />
    </telerik:RadScheduler.ViewDefinitions>
</telerik:RadScheduler>

3. Navigate to that page
4. Observe the unhandled exception

Expected Behavior:

The scheduler renders correctly with the AgendaViewDefinition, as it did in 13.0.0.

Actual Behavior:

An unhandled NullReferenceException is thrown:

System.NullReferenceException: Object reference not set to an instance of an object.
   at Telerik.Maui.Controls.Scheduler.SchedulerAgendaView.Init()
   at System.Threading.Tasks.Task.<>c.<ThrowAsync>b__124_0(Object state)
   at Microsoft.UI.Dispatching.DispatcherQueueSynchronizationContext.<>c__DisplayClass2_0.<Post>b__0()

Root Cause Analysis (via ILSpy decompilation):

Comparing the decompiled assemblies of 13.0.0 and 13.2.0 reveals a new override in RadScheduler introduced in 13.2.0:

// NEW in 13.2.0 — not present in 13.0.0:
protected override void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
    base.OnPropertyChanged(propertyName);
    if (propertyName == "Parent" && Parent != null && !IsLoaded)
        UpdateActiveViewDefinition();
}

This causes the following call chain to be triggered during InitializeComponent() in the page constructor — before the page is attached to a window:

1. XAML parser adds RadScheduler to the page → Parent property changes
2. OnPropertyChanged("Parent") fires → UpdateActiveViewDefinition() is called
3. → ActiveViewDefinition = ViewDefinitions[0] (the AgendaViewDefinition)
4. → OnActiveViewDefinitionChanged() → content.Rebuild() (template already applied on WinUI3)
5. → SchedulerAgendaView.Model setter → Init() is called as async void
6. Inside Init(), after the first await, the continuation runs and DataBindingComplete fires
7. The completeHandler inside Init() calls:

((BindableObject)this).Dispatcher.Dispatch(async delegate { ... });

8. Dispatcher is null because the SchedulerAgendaView is not yet attached to a window → NullReferenceException

The exception is captured by the async void state machine and re-thrown via SynchronizationContext.ThrowAsync → DispatcherQueueSynchronizationContext.Post, which matches the observed stack trace exactly.

Why it worked in 13.0.0: UpdateActiveViewDefinition() was never called from OnPropertyChanged. It was only invoked after IsLoaded = true, at which point Dispatcher is guaranteed to be non-null.

Why the condition !IsLoaded is insufficient: Parent != null does not imply a window is present. During InitializeComponent(), the element has a parent in the logical tree but is not yet attached to any Window, making Dispatcher null on BindableObject.

Workaround:

Do not declare ViewDefinitions in XAML. Instead, add them programmatically in the page's Loaded event handler, at which point Dispatcher is guaranteed to be available:

private void OnPageLoaded(object sender, EventArgs e)
{
    if (scheduler.ViewDefinitions.Count == 0)
    {
        scheduler.ViewDefinitions.Add(new AgendaViewDefinition());
        scheduler.ViewDefinitions.Add(new DayViewDefinition());
        scheduler.ViewDefinitions.Add(new WeekViewDefinition());
        scheduler.ViewDefinitions.Add(new MonthViewDefinition());
    }
}

Suggested Fix:

Either:

Option A — Guard Dispatcher usage inside SchedulerAgendaView.Init():

// In completeHandler, before calling Dispatch:
if (((BindableObject)this).Dispatcher is { } dispatcher)
    dispatcher.Dispatch(...);

Option B — Guard UpdateActiveViewDefinition() in RadScheduler.OnPropertyChanged to only run when content (the internal RadSchedulerContent) has already been set (i.e., template was applied):

if (propertyName == "Parent" && Parent != null && !IsLoaded && content != null)
    UpdateActiveViewDefinition();

Option B is more conservative and closer to the original 13.0.0 behavior, since content being non-null implies the template has been applied and Dispatcher is available.

Environment:

Right to left flow direction completely breaks the RadDataGrid on Android and on iOS it doesn't seem to do anything.

Repro steps:

Android:

1. Download project from github: Kbperri/RadDataGridBug
2. Run the app on an Android device
3. See that the DataGrid is showing up
4. Click the "Click me" button which sets the FlowDirection
5. See that the DataGrid disappears
6. Click the button again and it appears again

iOS:

1. Download project from github: Kbperri/RadDataGridBug
2. Run the app on an iOS device
3. See that the DataGrid is showing up
4. Click the "Click me" button which sets the FlowDirection
5. See that the DataGrid doesn't change direction

If you test this on Windows, the FlowDirection is being appropriately applied.

Android LTR:

RTL:

when building an app without explicitly setting the target platform, the following error appears:

The type or namespace name 'Compatibility' does not exist in the namespace 'Telerik.Maui.Controls' (are you missing an assembly reference?)

The Telerik.Maui.Controls.Compatibility dll is missing from the .net9/10 shared folders

Hi,

Do you have on your roadmap to include a Shimmer View / Control as part of your .NET MAUI offerings to tidy up a screen loading indication.

From a UI/UX perspective, a shimmer sits better with our user community rather than a loading indicator.

Thank you,

Shane

It seems the issue happens randomly -> crashes on a Windows 19 Server while running a basic Windows Maui app.

There is a public bug report: https://github.com/mono/SkiaSharp/issues/3168   

The Bottom Sheet component provides an intuitive way to display additional content to the users. It appears on the bottom of a screen as an overlay and presents users with a choice of actions that they must take.

When navigating to a page with a RadRichTextEditor, it sometimes pops up an error on page load.  It is inconsistent, but I attached an example gif.  The xaml on the page I'm navigating to is basic:

I believe this problem started with MAUI version 9.0.70.  Possibly with one of these changes:

https://github.com/dotnet/maui/pull/27003/files

https://github.com/dotnet/maui/pull/28354/files

Provide an AI assistant for code generation with the Telerik MAUI controls. 

Telerik Blazor released such assistant https://www.telerik.com/blazor-ui/documentation/ai/overview 

add a button control in which you can swipe its content 

I have a user who reported a crash. In Sentry, I see this:

System.NullReferenceException: Object reference not set to an instance of an object.
  ?, in void TelerikLicense.ShowLicenseMessage(Page page)
  ?, in void TelerikLicense.VerifyLicense(Element element)+() => { }
  ?, in void TelerikLicense.ExecuteActionOnLoaded(Page page, Action action)
  ?, in void TelerikLicense.VerifyLicense(Element element)
  ?, in object <InitializeComponent>_anonXamlCDataTemplate_21.LoadDataTemplate()
  ?, in object ElementTemplate.CreateContent()
  ?, in void BindableLayoutController.CreateChildren()
  ?, in NotifyCollectionChangedAction NotifyCollectionChangedEventArgsExtensions.Apply(NotifyCollectionChangedEventArgs self, Action<object, int, bool> insert, Action<object, int> removeAt, Action reset)
  ?, in void BindableLayoutController.ItemsSourceCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
  ?, in void WeakNotifyCollectionChangedProxy.OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
  File "ObservableCollection.cs", line 192, in void ObservableCollection<T>.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
    handler(this, e);
  ?, in void ExtObservableCollection<T>.RaiseCollectionChanged()
the app was built with a successful license-check
Telerik.Licensing 1.6.6
 

Hi Team,

We have a scenario where our license key file is hosted on a team-only file share. However, the file share only works with HTTP/S links and not a UNC path.

For example, this works perfectly:

TELERIK_LICENSE_PATH="\\internalshare\folder\telerik-license.txt"

However, we cannot use 

TELERIK_LICENSE_PATH="http://internalshare.com/telerik-license.txt"

Thank you,

Teddy