spectreconsole/spectre.console · error · ArgumentNullException

Value cannot be null. (Parameter 'content')

Error message

Value cannot be null. (Parameter 'content')

What it means

Thrown by the Panel(IRenderable) constructor when the content argument is null. A Panel requires a child renderable to draw inside its border. Note the string overload delegates to new Markup(text) which itself handles null text.

Source

Thrown at src/Spectre.Console/Widgets/Panel.cs:68

    /// </summary>
    internal bool Inline { get; set; }

    /// <summary>
    /// Initializes a new instance of the <see cref="Panel"/> class.
    /// </summary>
    /// <param name="text">The panel content.</param>
    public Panel(string text)
        : this(new Markup(text))
    {
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="Panel"/> class.
    /// </summary>
    /// <param name="content">The panel content.</param>
    public Panel(IRenderable content)
    {
        _child = content ?? throw new ArgumentNullException(nameof(content));
    }

    /// <inheritdoc/>
    protected override Measurement Measure(RenderOptions options, int maxWidth)
    {
        var child = new Padder(_child, Padding);
        return Measure(options, maxWidth, child);
    }

    private Measurement Measure(RenderOptions options, int maxWidth, IRenderable child)
    {
        var edgeWidth = (options.GetSafeBorder(this) is not NoBoxBorder) ? EdgeWidth : 0;
        var childWidth = child.Measure(options, maxWidth - edgeWidth);

        if (Width != null)
        {
            var width = Width.Value - edgeWidth;

View on GitHub (pinned to 0acc92fada)

Solutions

1. Pass a non-null IRenderable such as new Text("...") or new Markup("...").
2. Use the string overload 'new Panel(text)' which tolerates null via Markup.
3. Null-check before constructing the Panel.

Example fix

// before
var panel = new Panel(maybeNullRenderable);

// after
var panel = new Panel(maybeNullRenderable ?? new Text(string.Empty));

if (content is null) throw new ArgumentNullException(nameof(content));
var panel = new Panel(content);

static bool HasValidPanelContent(IRenderable? content) => content is not null;

When it happens

Trigger: Constructing 'new Panel((IRenderable)null)' or passing a variable of type IRenderable that is null.

Common situations: Passing a renderable obtained from a method that returned null, or an optional content variable that was not set.

Related errors

• Value cannot be null. (Parameter 'text')
• Value cannot be null. (Parameter 'children')
• Value cannot be null. (Parameter 'title')
• Value cannot be null. (Parameter 'content')
• Must be > 1

AI-assisted analysis of spectreconsole/spectre.console@0acc92fada (2026-08-13). Data as JSON: /api/errors/6988dfb6ac1b6529. Report an issue: GitHub.