dotnet/maui · error · ArgumentException

'{0}' Transition could not be found!

Error message

'{0}' Transition could not be found!

What it means

FormsTransitioningContentControl throws ArgumentException("'{0}' Transition could not be found!") when GetStoryboard(Transition) returns null, meaning the named Transition DependencyProperty does not map to a VisualState storyboard in the control's VSM groups. The control reverts Transition to DefaultTransitionState before throwing.

Source

Thrown at src/Compatibility/Core/src/WPF/Controls/FormsTransitioningContentControl.cs:247

					this.currentContentPresentationSite.ContentTemplate = this.ContentTemplateSelector.SelectTemplate(this.Content, this);
				}
				else
				{
					this.currentContentPresentationSite.ContentTemplate = this.ContentTemplate;
				}
				this.currentContentPresentationSite.Content = this.Content;
			}

			// hookup currenttransition
			Storyboard transition = this.GetStoryboard(this.Transition);
			this.CurrentTransition = transition;
			if (transition == null)
			{
				var invalidTransition = this.Transition;
				// revert to default
				this.Transition = DefaultTransitionState;

				throw new ArgumentException(string.Format("'{0}' Transition could not be found!", invalidTransition), "Transition");
			}
			System.Windows.VisualStateManager.GoToState(this, NormalState, false);
		}

		protected override void OnContentChanged(object oldContent, object newContent)
		{
			base.OnContentChanged(oldContent, newContent);

			this.StartTransition(oldContent, newContent);
		}

		[SuppressMessage("Microsoft.Usage", "CA1801:ReviewUnusedParameters", MessageId = "newContent", Justification = "Should be used in the future.")]
		private void StartTransition(object oldContent, object newContent)
		{
			// both presenters must be available, otherwise a transition is useless.
			if (this.currentContentPresentationSite != null && this.previousContentPresentationSite != null)
			{
				if (this.RestartTransitionOnContentChange)

View on GitHub (pinned to f377ff1c5e)

Solutions

1. Confirm the ControlTemplate defines a VisualStateGroup containing the named VisualState.
2. Set Transition only after the template is applied (OnApplyTemplate) so VSM groups exist.
3. Use one of the well-known state names (DefaultTransitionState) if uncertain.
4. Catch ArgumentException during dynamic theme switches and fall back to the default transition.

Example fix

// before
control.Transition = "SlideIn"; // no such state -> throws

// after
var group = VisualStateManager.GetVisualStateGroups(control).OfType<VisualStateGroup>().FirstOrDefault(g => g.Name == "CommonStates");
if (group?.States.Any(s => s.Name == "SlideIn") == true)
    control.Transition = "SlideIn";
else
    control.Transition = FormsTransitioningContentControl.DefaultTransitionState;

if (control.GetStoryboard(name) != null) control.Transition = name;
else control.Transition = FormsTransitioningContentControl.DefaultTransitionState;

static bool TransitionExists(FormsTransitioningContentControl c, string name) => c.GetStoryboard(name) != null;

try { control.Transition = name; }
catch (ArgumentException ex) when (ex.ParamName == "Transition")
{ control.Transition = FormsTransitioningContentControl.DefaultTransitionState; }

When it happens

Trigger: Setting Transition to a state name absent from the control's VisualStateManager groups; referencing a state from a different template; template applied late so states are missing when ApplyTransition runs.

Common situations: Custom ControlTemplate missing the expected VisualStateGroup/States; XAML binds Transition to a value from a config that drifts from the template; theme/template swapped without updating Transition names.

Related errors

• Temporary removed exception message
• The element must be a DependencyObject
• Unable to find the required services. Please add all the req
• RootComponent requires a value for its Selector property, bu
• RootComponent requires a value for its ComponentType propert

AI-assisted analysis of dotnet/maui@f377ff1c5e (2026-08-13). Data as JSON: /api/errors/6e609b56c0caec37. Report an issue: GitHub.