HandyControl/src/Shared/HandyControl_Shared/Controls/Other/Gravatar.cs

using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using HandyControl.Tools;

namespace HandyControl.Controls
{
    public class Gravatar : ContentControl
    {
        public static readonly DependencyProperty GeneratorProperty = DependencyProperty.Register(
            "Generator", typeof(IGravatarGenerator), typeof(Gravatar), new PropertyMetadata(new GithubGravatarGenerator()));

        public IGravatarGenerator Generator
        {
            get => (IGravatarGenerator) GetValue(GeneratorProperty);
            set => SetValue(GeneratorProperty, value);
        }

        public static readonly DependencyProperty IdProperty = DependencyProperty.Register(
            "Id", typeof(string), typeof(Gravatar), new PropertyMetadata(default(string), OnIdChanged));

        private static void OnIdChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var ctl = (Gravatar) d;
            if (ctl.Source != null) return;
            ctl.Content = ctl.Generator.GetGravatar((string)e.NewValue);
        }

        public string Id
        {
            get => (string) GetValue(IdProperty);
            set => SetValue(IdProperty, value);
        }

        public static readonly DependencyProperty SourceProperty = DependencyProperty.Register(
            "Source", typeof(ImageSource), typeof(Gravatar), new PropertyMetadata(default(ImageSource), OnSourceChanged));

        private static void OnSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var ctl = (Gravatar)d;
            var v = (ImageSource) e.NewValue;

            ctl.Background = v != null
                ? new ImageBrush(v)
                {
                    Stretch = Stretch.UniformToFill
                }
                : ResourceHelper.GetResource<Brush>("SecondaryRegionBrush");
        }

        public ImageSource Source
        {
            get => (ImageSource) GetValue(SourceProperty);
            set => SetValue(SourceProperty, value);
        }
    }
}