MaterialDesignInXAML/MaterialDesignInXamlToolkit · error · ArgumentNullException

All action arguments must be provided if any are provided.

Error message

All action arguments must be provided if any are provided.

What it means

The generic Enqueue<TArgument> overload requires actionContent and actionHandler to be both present or both absent (an XOR check). Supplying only one half would show a button with no handler or wire a handler with no button, so it throws ArgumentNullException naming the missing half.

Source

Thrown at src/MaterialDesignThemes.Wpf/SnackbarMessageQueue.cs:186

    public void Enqueue(object content, object? actionContent, Action? actionHandler, bool promote)
        => Enqueue(content, actionContent, _ => actionHandler?.Invoke(), false, promote, false);

    public void Enqueue<TArgument>(object content, object? actionContent, Action<TArgument?>? actionHandler,
        TArgument? actionArgument)
        => Enqueue(content, actionContent, actionHandler, actionArgument, false, false);

    public void Enqueue<TArgument>(object content, object? actionContent, Action<TArgument?>? actionHandler,
        TArgument? actionArgument, bool promote) =>
        Enqueue(content, actionContent, actionHandler, actionArgument, promote, false);

    public void Enqueue<TArgument>(object content, object? actionContent, Action<TArgument?>? actionHandler,
        TArgument? actionArgument, bool promote, bool neverConsiderToBeDuplicate, TimeSpan? durationOverride = null)
    {
        if (content is null) throw new ArgumentNullException(nameof(content));

        if (actionContent is null ^ actionHandler is null)
        {
            throw new ArgumentNullException(actionContent != null ? nameof(actionContent) : nameof(actionHandler),
                "All action arguments must be provided if any are provided.");
        }

        Action<object?>? handler = actionHandler != null
            ? new Action<object?>(argument => actionHandler((TArgument?)argument))
            : null;
        Enqueue(content, actionContent, handler, actionArgument, promote, neverConsiderToBeDuplicate, durationOverride);
    }

    public void Enqueue(object content, object? actionContent, Action<object?>? actionHandler,
        object? actionArgument, bool promote, bool neverConsiderToBeDuplicate, TimeSpan? durationOverride = null)
    {
        if (content is null) throw new ArgumentNullException(nameof(content));

        if (actionContent is null ^ actionHandler is null)
        {
            throw new ArgumentNullException(actionContent != null ? nameof(actionContent) : nameof(actionHandler),
                "All action arguments must be provided if any are provided.");

View on GitHub (pinned to 98edec3a0b)

Solutions

1. Provide both actionContent and actionHandler, or pass null for both.
2. If no action is needed, use the simpler Enqueue(content) overload.
3. Centralize snackbar action creation in a helper that always pairs content and handler.

Example fix

// before
queue.Enqueue("Saved", "Undo", null);
// after
queue.Enqueue("Saved", "Undo", () => Revert());

bool hasAction = actionContent is not null;
bool hasHandler = actionHandler is not null;
if (hasAction != hasHandler)
    throw new ArgumentException("Provide both actionContent and actionHandler, or neither.");
queue.Enqueue(content, actionContent, actionHandler, arg, promote);

(actionContent is null) == (actionHandler is null)

When it happens

Trigger: Calling Enqueue<TArgument> with actionContent set but actionHandler null, or actionHandler set but actionContent null.

Common situations: Wiring an action button but forgetting the callback delegate; a refactor that removed the handler; conditionally providing only the button text.

Related errors

• content
• session
• session
• window
• childDependencyObject

AI-assisted analysis of MaterialDesignInXAML/MaterialDesignInXamlToolkit@98edec3a0b (2026-08-13). Data as JSON: /api/errors/f16b71c9896e9438. Report an issue: GitHub.