Avalonia/src/Avalonia.Styling/Styling/StyleExtensions.cs

// Copyright (c) The Avalonia Project. All rights reserved.
// Licensed under the MIT license. See licence.md file in the project root for full license information.

using System;

namespace Avalonia.Styling
{
    public static class StyleExtensions
    {
        /// <summary>
        /// Tries to find a named style resource.
        /// </summary>
        /// <param name="control">The control from which to find the resource.</param>
        /// <param name="name">The resource name.</param>
        /// <returns>
        /// The resource if found, otherwise <see cref="AvaloniaProperty.UnsetValue"/>.
        /// </returns>
        public static object FindStyleResource(this IStyleHost control, string name)
        {
            Contract.Requires<ArgumentNullException>(control != null);
            Contract.Requires<ArgumentNullException>(name != null);
            Contract.Requires<ArgumentException>(!string.IsNullOrWhiteSpace(name));

            while (control != null)
            {
                if (control.IsStylesInitialized)
                {
                    var result = control.Styles.FindResource(name);

                    if (result != AvaloniaProperty.UnsetValue)
                    {
                        return result;
                    }
                }

                control = control.StylingParent;
            }

            return AvaloniaProperty.UnsetValue;
        }
    }
}