MaterialDesignInXAML/MaterialDesignInXamlToolkit · error · ArgumentException

Non primary hues provided.

Error message

Non primary hues provided.

What it means

`Swatch` (MaterialDesignColors.Wpf) represents a named colour swatch and requires at least one primary hue to pick an `ExemplarHue`. Its constructor throws `ArgumentException` if `primaryHues` resolves to an empty list, because the exemplar lookup `primaryHuesList[ExemplarHueIndex]` would otherwise throw `ArgumentOutOfRangeException`.

Source

Thrown at src/MaterialDesignColors.Wpf/Swatch.cs:15

namespace MaterialDesignColors;

/// <summary>
/// Defines a single colour swatch.
/// </summary>
public class Swatch
{
    public Swatch(string name, IEnumerable<Hue> primaryHues, IEnumerable<Hue> secondaryHues)
    {
        if (name is null) throw new ArgumentNullException(nameof(name));
        if (primaryHues is null) throw new ArgumentNullException(nameof(primaryHues));
        if (secondaryHues is null) throw new ArgumentNullException(nameof(secondaryHues));

        var primaryHuesList = primaryHues.ToList();
        if (primaryHuesList.Count == 0) throw new ArgumentException("Non primary hues provided.", nameof(primaryHues));

        Name = name;
        PrimaryHues = primaryHuesList;
        var secondaryHuesList = secondaryHues.ToList();
        SecondaryHues = secondaryHuesList;
        ExemplarHue = primaryHuesList[ExemplarHueIndex];
        if (SecondaryHueIndex >= 0 && SecondaryHueIndex < secondaryHuesList.Count)
        {
            SecondaryExemplarHue = secondaryHuesList[SecondaryHueIndex];
        }
    }

    public string Name { get; }

    public Hue ExemplarHue { get; }

    public Hue? SecondaryExemplarHue { get; }

View on GitHub (pinned to 98edec3a0b)

Solutions

1. Ensure the primaryHues collection passed to the `Swatch` constructor contains at least one `Hue`.
2. Skip/handle the empty case upstream: `if (!primaryHues.Any()) continue;` before constructing the swatch.
3. If building a custom `SwatchesProvider`, validate the resource assembly actually defines primary hue entries.
4. Unit-test custom swatch generation against empty inputs.

Example fix

// before
var swatch = new Swatch("Red", Enumerable.Empty<Hue>(), secondaryHues); // throws

// after
var primaryHues = BuildPrimaryHues();
if (primaryHues.Count == 0) continue;
var swatch = new Swatch("Red", primaryHues, secondaryHues);

var primary = BuildPrimaryHues();
if (primary is null || primary.Count == 0) continue;
var swatch = new Swatch(name, primary, secondary);

static bool HasPrimaryHues(IEnumerable<Hue> hues)
    => hues is not null && hues.Any();

When it happens

Trigger: Constructing `new Swatch(name, primaryHues, secondaryHues)` with `primaryHues` being an empty enumeration (e.g. `Enumerable.Empty<Hue>()` or a filtered list that yielded nothing).

Common situations: A custom swatch provider that filters hues and returns none; a malformed/empty theme resource assembly; code that builds swatches dynamically and passes an empty source collection.

Related errors

• kinds must contain at least one value
• Entry {entry.Key} was not of type Color
• Entry {foregroundKey} was not of type Color
• MinuteSelectionStep must be a divisor of 60 and between 1 an
• ColorReference does not contain any color

AI-assisted analysis of MaterialDesignInXAML/MaterialDesignInXamlToolkit@98edec3a0b (2026-08-13). Data as JSON: /api/errors/c55a72b907bfb3bb. Report an issue: GitHub.