stride3d/stride · error · ArgumentNullException

Value cannot be null. (Parameter 'metadatas')

Error message

Value cannot be null. (Parameter 'metadatas')

What it means

The metadatas parameter of DependencyPropertyFactory.Register is declared as a params array but is still explicitly null-checked; passing an explicit null array is treated as a programming mistake. The factory throws ArgumentNullException(nameof(metadatas)) before registering the property.

Solutions

1. Omit the metadata arguments entirely (params allows zero arguments) instead of passing null
2. Pass an empty array: Array.Empty<PropertyKeyMetadata>()
3. In wrappers, default null metadata lists to an empty array before forwarding

Example fix

// before
DependencyPropertyFactory.Register("P", typeof(C), 0, null, null, (PropertyKeyMetadata[])null); // throws
// after
DependencyPropertyFactory.Register("P", typeof(C), 0, null, null); // no metadata args

metadatas ??= Array.Empty<PropertyKeyMetadata>();

bool HasMetadata(PropertyKeyMetadata[] m) => m != null;

try
{
    key = DependencyPropertyFactory.Register(name, ownerType, defaultValue, null, null, metadatas);
}
catch (ArgumentNullException ex) when (ex.ParamName == "metadatas")
{
    // supply an empty array or correct metadata
}

When it happens

Trigger: Calling Register<T>(...) with an explicitly cast null: metadatas: (PropertyKeyMetadata[])null; invoking the method via reflection or a delegate that supplies a null array; an overload shim forwarding a null metadata list.

Common situations: Reflection-driven property registration frameworks; generic wrappers around Register that pass their metadata parameter straight through when unset.

Related errors

• Value cannot be null. (Parameter 'ownerType')
• Title can not be null
• texture
• font
• Value cannot be null. (Parameter 'name')

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/709c80aa28f464a5. Report an issue: GitHub.

Appendix: source

Thrown at sources/engine/Stride.UI/DependencyPropertyFactory.cs:72

            return Register(name, ownerType, defaultValue, null, invalidationCallback);
        }

        /// <summary>
        /// Registers a dependency property.
        /// </summary>
        /// <typeparam name="T">The type of the property.</typeparam>
        /// <param name="name">The name of the property.</param>
        /// <param name="ownerType">The type that is registering the property.</param>
        /// <param name="defaultValue">The default value of the property.</param>
        /// <param name="validateValueCallback">A callback for validation/coercision of the property's value.</param>
        /// <param name="invalidationCallback">A callback to invalidate an object state after a modification of the property's value.</param>
        /// <param name="metadatas">The metadatas.</param>
        /// <returns></returns>
        public static PropertyKey<T> Register<T>(string name, Type ownerType, T defaultValue, ValidateValueCallback<T> validateValueCallback, ObjectInvalidationCallback<T> invalidationCallback, params PropertyKeyMetadata[] metadatas)
        {
            if (name == null) throw new ArgumentNullException(nameof(name));
            if (ownerType == null) throw new ArgumentNullException(nameof(ownerType));
            if (metadatas == null) throw new ArgumentNullException(nameof(metadatas));

            return RegisterCommon(DependencyPropertyKeyMetadata.Default, name, ownerType, defaultValue, validateValueCallback, invalidationCallback, metadatas);
        }

        /// <summary>
        /// Registers an attached dependency property.
        /// </summary>
        /// <typeparam name="T">The type of the property.</typeparam>
        /// <param name="name">The name of the property.</param>
        /// <param name="ownerType">The type that is registering the property.</param>
        /// <param name="defaultValue">The default value of the property.</param>
        /// <returns></returns>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static PropertyKey<T> RegisterAttached<T>(string name, Type ownerType, T defaultValue)
        {
            return RegisterAttached(name, ownerType, defaultValue, null, null);
        }

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