MaterialDesignInXAML/MaterialDesignInXamlToolkit · error · XamlParseException

Could not parse to type {typeof(TransitionEffectKind).FullNa

Error message

Could not parse to type {typeof(TransitionEffectKind).FullName} or {typeof(TransitionEffectBase).FullName}.

What it means

TransitionEffectTypeConverter converts a XAML attribute into a TransitionEffectBase. It first tries Enum.TryParse on the string against TransitionEffectKind; failing that it attempts to cast the value to TransitionEffectBase. If both fail it throws XamlParseException naming both candidate types, surfacing a clear load-time error rather than a silent wrong transition.

Source

Thrown at src/MaterialDesignThemes.Wpf/Transitions/TransitionEffectTypeConverter.cs:28

        return sourceType == typeof(string) || typeof(TransitionEffectKind).IsAssignableFrom(sourceType);
    }

    public override object? ConvertFrom(ITypeDescriptorContext? context, CultureInfo? culture, object value)
    {
        TransitionEffectBase? transitionEffect;

        if (value is string stringValue &&
            Enum.TryParse(stringValue, out TransitionEffectKind effectKind))
        {
            transitionEffect = new TransitionEffect(effectKind);
        }
        else
        {
            transitionEffect = value as TransitionEffectBase;
        }

        if (transitionEffect is null)
            throw new XamlParseException($"Could not parse to type {typeof(TransitionEffectKind).FullName} or {typeof(TransitionEffectBase).FullName}.");

        return transitionEffect;
    }
}

View on GitHub (pinned to 98edec3a0b)

Solutions

Use a valid TransitionEffectKind name (e.g. 'FadeIn', 'SlideInFromLeft', 'Expand').
Check the TransitionEffectKind enum in your installed version for the exact available names.
Assign a TransitionEffect or other TransitionEffectBase instance instead of a string.

Example fix

<!-- before -->
<md:TransitioningContent TransitionEffect="FadeInn" />
<!-- after -->
<md:TransitioningContent TransitionEffect="FadeIn" />

Defensive patterns

Strategy: validation

Validate before calling

if (!Enum.TryParse<TransitionEffectKind>(stringValue, out _))
    throw new ArgumentException($"'{stringValue}' is not a valid TransitionEffectKind.");
// then set the property / use the converter

Type guard

Enum.TryParse<TransitionEffectKind>(stringValue, out _)

Prevention

Cross-check transition names against the TransitionEffectKind enum for your version.
Assign a TransitionEffectBase instance when the kind is dynamic.
Validate user-supplied transition strings before binding them to the property.

When it happens

Trigger: Setting a transition-related attribute in XAML to a string that is not a valid TransitionEffectKind name and is not a TransitionEffectBase instance; the exception appears at XAML load/parse time.

Common situations: Typos in transition names (e.g. 'FadeInn'); using an enum name that was renamed/removed after a version upgrade; assigning a non-transition object to the property.

Related errors

AI-assisted analysis of MaterialDesignInXAML/MaterialDesignInXamlToolkit@98edec3a0b (2026-08-13). Data as JSON: /api/errors/6c261ffa53a9b0b6. Report an issue: GitHub.