HandyOrg/HandyControl · error · ArgumentException

ExceptionStringTable.DefaultTriggerAttributeInvalidTriggerTy…

Error message

ExceptionStringTable.DefaultTriggerAttributeInvalidTriggerTypeSpecifiedExceptionMessage

What it means

The DefaultTriggerAttribute constructor requires its triggerType parameter to be a type deriving from TriggerBase. Passing any other Type throws ArgumentException DefaultTriggerAttributeInvalidTriggerTypeSpecifiedExceptionMessage with the offending type name.

Solutions

Pass a Type that derives from TriggerBase (e.g. typeof(EventTrigger), typeof(PropertyChangedTrigger)).
Verify the trigger type's namespace — Microsoft.Xaml.Behaviors TriggerBase, not a same-named custom class.
Ensure custom triggers inherit from TriggerBase before referencing them in DefaultTriggerAttribute.
Fix the constructor call if invoking DefaultTriggerAttribute directly via reflection or codegen.

Example fix

// before
[DefaultTrigger(typeof(Button), typeof(Button), "Click")]
// after
[DefaultTrigger(typeof(Button), typeof(EventTrigger), "Click")]

Defensive patterns

Strategy: validation

Validate before calling

if (triggerType == null || !typeof(TriggerBase).IsAssignableFrom(triggerType))
    throw new ArgumentException($"{triggerType?.Name} must derive from TriggerBase");

Type guard

static bool IsValidTriggerType(Type t) => t != null && typeof(TriggerBase).IsAssignableFrom(t);

Try / catch

try { var attr = new DefaultTriggerAttribute(targetType, triggerType); }
catch (ArgumentException ex) when (ex.Message.Contains("InvalidTriggerType")) { /* fix trigger type */ }

Prevention

Only pass TriggerBase-derived types to DefaultTriggerAttribute.
Compile-time: reference the exact trigger class in the attribute.
Watch for same-named classes in different namespaces.
Ensure custom triggers inherit TriggerBase.

When it happens

Trigger: Writing [DefaultTrigger(typeof(Button), typeof(SomeNonTriggerType), ...)] or calling new DefaultTriggerAttribute(targetType, triggerType, params) with a triggerType where typeof(TriggerBase).IsAssignableFrom(triggerType) is false.

Common situations: Typo or autocomplete picking an EventTrigger from the wrong namespace; passing the target class itself as the trigger type; copy-pasting an attribute line and forgetting to change the trigger type; using TriggerAction-derived types by mistake.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

AI-assisted analysis of HandyOrg/HandyControl@2c0875ebd6 (2026-09-14). Data as JSON: /api/errors/5bfba4a966d76dc9. Report an issue: GitHub.

Appendix: source

Thrown at src/Shared/System.Windows.Interactivity/DefaultTriggerAttribute.cs:20

using System.Collections;
using System.Globalization;

namespace HandyControl.Interactivity;

[AttributeUsage(AttributeTargets.Property | AttributeTargets.Class, AllowMultiple = true)]
public sealed class DefaultTriggerAttribute : Attribute
{
    private readonly object[] _parameters;

    public DefaultTriggerAttribute(Type targetType, Type triggerType, object parameter) : this(targetType,
        triggerType, new[] { parameter })
    {
    }

    public DefaultTriggerAttribute(Type targetType, Type triggerType, params object[] parameters)
    {
        if (!typeof(TriggerBase).IsAssignableFrom(triggerType))
            throw new ArgumentException(string.Format(CultureInfo.CurrentCulture,
                ExceptionStringTable.DefaultTriggerAttributeInvalidTriggerTypeSpecifiedExceptionMessage,
                new object[] { triggerType.Name }));
        TargetType = targetType;
        TriggerType = triggerType;
        _parameters = parameters;
    }

    public IEnumerable Parameters =>
        _parameters;

    public Type TargetType { get; }

    public Type TriggerType { get; }

    public TriggerBase Instantiate()
    {
        object obj2 = null;
        try

View on GitHub (pinned to 2c0875ebd6)