Avalonia/src/Markup/Avalonia.Markup.Xaml/Extensions.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using Avalonia.Controls;
using Avalonia.Markup.Xaml.XamlIl.Runtime;
using Avalonia.Styling;

namespace Avalonia.Markup.Xaml
{
    internal static class Extensions
    {
        public static T GetService<T>(this IServiceProvider sp) => (T)sp?.GetService(typeof(T));
        
        
        public static Uri GetContextBaseUri(this IServiceProvider ctx) => ctx.GetService<IUriContext>().BaseUri;

        public static T GetFirstParent<T>(this IServiceProvider ctx) where T : class 
            => ctx.GetService<IAvaloniaXamlIlParentStackProvider>().Parents.OfType<T>().FirstOrDefault();

        public static T GetLastParent<T>(this IServiceProvider ctx) where T : class 
            => ctx.GetService<IAvaloniaXamlIlParentStackProvider>().Parents.OfType<T>().LastOrDefault();

        public static IEnumerable<T> GetParents<T>(this IServiceProvider sp)
        {
            return sp.GetService<IAvaloniaXamlIlParentStackProvider>().Parents.OfType<T>();
            
            
        }

        public static Type ResolveType(this IServiceProvider ctx, string namespacePrefix, string type)
        {
            var tr = ctx.GetService<IXamlTypeResolver>();
            string name = string.IsNullOrEmpty(namespacePrefix) ? type : $"{namespacePrefix}:{type}";
            return tr?.Resolve(name);
        }
        
        public static object GetDefaultAnchor(this IServiceProvider provider)
        {
            // If the target is not a control, so we need to find an anchor that will let us look
            // up named controls and style resources. First look for the closest IControl in
            // the context.
            object anchor = provider.GetFirstParent<IControl>();

            if (anchor is null)
            {
                // Try to find IDataContextProvider, this was added to allow us to find
                // a datacontext for Application class when using NativeMenuItems.
                anchor = provider.GetFirstParent<IDataContextProvider>();
            }

            // If a control was not found, then try to find the highest-level style as the XAML
            // file could be a XAML file containing only styles.
            return anchor ??
                   provider.GetService<IRootObjectProvider>()?.RootObject as IStyle ??
                   provider.GetLastParent<IStyle>();
        }
    }
}