PackIconControl.cs

public class PackIconControl : ContentControl
{
    public PackIconControl()
    {
        SizeChanged += OnSizeChanged;
    }

    public static readonly DependencyProperty PackIconKindProperty =
        DependencyProperty.Register(nameof(PackIconKind), typeof(object), typeof(PackIconControl),
            new PropertyMetadata(default(object), PackIconKindPropertyChangedCallback));

    private static void PackIconKindPropertyChangedCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
    {
        PackIconBase newContent;
        switch (dependencyPropertyChangedEventArgs.NewValue)
        {
            case PackIconEntypoKind kind:
                newContent = new PackIconEntypo { Kind = kind };
                break;
            case PackIconFontAwesomeKind kind:
                newContent = new PackIconFontAwesome { Kind = kind };
                break;
            case PackIconMaterialKind kind:
                newContent = new PackIconMaterial { Kind = kind };
                break;
            case PackIconMaterialLightKind kind:
                newContent = new PackIconMaterialLight { Kind = kind };
                break;
            case PackIconModernKind kind:
                newContent = new PackIconModern { Kind = kind };
                break;
            case PackIconOcticonsKind kind:
                newContent = new PackIconOcticons { Kind = kind };
                break;
            case PackIconSimpleIconsKind kind:
                newContent = new PackIconSimpleIcons { Kind = kind };
                break;
            default:
                newContent = null;
                break;
        }
        
        var control = (PackIconControl)dependencyObject;
        if (newContent != null)
        {
            newContent.Width = control.Width;
            newContent.Height = control.Height;
        }

        control.Content = newContent;
    }

    public object PackIconKind
    {
        get => GetValue(PackIconKindProperty);
        set => SetValue(PackIconKindProperty, value);
    }

    private void OnSizeChanged(object sender, SizeChangedEventArgs e)
    {
        if (Content is PackIconBase content)
        {
            content.Width = Width;
            content.Height = Height;
        }
    }
}