What causes "PropertyName must be set." in stride3d/stride?

Set the PropertyName property on the behavior to the exact name of the target dependency property, e.g. PropertyName="Text".

stride3d/stride · error · ArgumentException

PropertyName must be set.

Error message

PropertyName must be set.

What it means

OnFocusBindingInterruptionBehavior interrupts a WPF binding on a dependency property while the element has keyboard focus, so typed input is not overwritten by binding updates. In OnAttached it first validates that the PropertyName behavior property is a non-empty, non-whitespace string. If it was never set (or is blank), it throws ArgumentException to fail fast instead of producing a silently non-functional behavior.

Solutions

Set the PropertyName property on the behavior to the exact name of the target dependency property, e.g. PropertyName="Text".
Verify PropertyName is not empty or whitespace at runtime before the element loads (e.g. if set via binding/data, ensure it evaluates before OnAttached).
If the behavior is not needed, remove it from the interaction Behaviors collection entirely instead of leaving an unconfigured instance.

Example fix

<!-- before -->
<i:Interaction.Behaviors>
  <b:OnFocusBindingInterruptionBehavior Binding="{Binding Name}" />
</i:Interaction.Behaviors>

<!-- after -->
<i:Interaction.Behaviors>
  <b:OnFocusBindingInterruptionBehavior PropertyName="Text" Binding="{Binding Name}" />
</i:Interaction.Behaviors>

Defensive patterns

Strategy: validation

Validate before calling

var behavior = new OnFocusBindingInterruptionBehavior();
if (string.IsNullOrWhiteSpace(behavior.PropertyName))
    throw new InvalidOperationException("Set PropertyName before attaching OnFocusBindingInterruptionBehavior.");

Try / catch

try { BehaviorCollectionHelper.Attach(behavior); }
catch (ArgumentException ex) when (ex.Message == "PropertyName must be set.") { log.Error("Behavior misconfigured: PropertyName missing"); }

Prevention

Always pair PropertyName and Binding attributes when using OnFocusBindingInterruptionBehavior in XAML.
Create a reusable XAML snippet/style that includes both required properties.
Review behaviors during code review for both required attributes before merging.

When it happens

Trigger: Attaching OnFocusBindingInterruptionBehavior via XAML or code without setting its PropertyName property, e.g. <behaviors:OnFocusBindingInterruptionBehavior Binding="{Binding SomePath}"/> with no PropertyName attribute, or setting PropertyName="" or whitespace.

Common situations: Copying the behavior usage from an example but deleting the PropertyName attribute; binding PropertyName to a resource/ViewModel value that resolves to empty at attach time; renaming the target property and clearing the attribute accidentally.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/3de5f31910dd61cd. Report an issue: GitHub.

Appendix: source

Thrown at sources/presentation/Stride.Core.Presentation.Wpf/Behaviors/OnFocusBindingInterruptionBehavior.cs:36

    /// <remarks>The host element must be of type <c>UIElement</c> and the <c>DependencyProprty</c> defined by PropertyName property must be set to a <c>BindingBase</c> object.</remarks>
    public class OnFocusBindingInterruptionBehavior : Behavior<DependencyObject>
    {
        private IDisposable subscriber;
        private DependencyProperty property;

        /// <summary>
        /// Gets or sets the name of the DependencyProperty on which the Binding has to be interrupted.
        /// </summary>
        public string PropertyName { get; set; }
        /// <summary>
        /// Gets or sets the binding to apply on the Host property defined by 'PropertyName' behavior property.
        /// </summary>
        public BindingBase Binding { get; set; }

        protected override void OnAttached()
        {
            if (string.IsNullOrWhiteSpace(PropertyName))
                throw new ArgumentException("PropertyName must be set.");

            if (Binding == null)
            {
                throw new ArgumentException($"Binding must be set for {PropertyName} property of host '{AssociatedObject}' on behavior '{GetType().FullName}'.");
            }

            property = AssociatedObject.GetDependencyProperties(true).FirstOrDefault(dp => dp.Name == PropertyName);

            if (property == null /* need to check DesignMode as well ? */)
                throw new InvalidOperationException($"Impossible to find property named '{PropertyName}' on object typed '{AssociatedObject.GetType()}'.");

            if ((Binding is Binding) == false)
                throw new InvalidOperationException("Not supported binding type.");

            var element = AssociatedObject as FrameworkElement;
            if (element == null)
            {
                throw new InvalidOperationException(

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