Create a shared project with all Win App common files (8.1 and 10)

Finally use the dependency injected Resource Service

WinAppCommon/Extensions/ColorExtensions.cs

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+using System.Drawing;
+using Windows.UI.Xaml.Media;
+
+namespace ModernKeePass.Extensions
+{
+    public static class ColorExtensions
+    {
+        public static Color ToColor(this SolidColorBrush brush)
+        {
+            return Color.FromArgb(brush.Color.A, brush.Color.R, brush.Color.G, brush.Color.B);
+        }
+
+        public static SolidColorBrush ToSolidColorBrush(this Color color)
+        {
+            return new SolidColorBrush(Windows.UI.Color.FromArgb(color.A, color.R, color.G, color.B));
+        }
+    }
+}

WinAppCommon/Extensions/DispatcherTaskExtensions.cs

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+using System;
+using System.Threading.Tasks;
+using Windows.UI.Core;
+
+namespace ModernKeePass.Extensions
+{
+    public static class DispatcherTaskExtensions
+    {
+        public static async Task<T> RunTaskAsync<T>(this CoreDispatcher dispatcher,
+            Func<Task<T>> func, CoreDispatcherPriority priority = CoreDispatcherPriority.Normal)
+        {
+            var taskCompletionSource = new TaskCompletionSource<T>();
+            await dispatcher.RunAsync(priority, async () =>
+            {
+                try
+                {
+                    taskCompletionSource.SetResult(await func());
+                }
+                catch (Exception ex)
+                {
+                    taskCompletionSource.SetException(ex);
+                }
+            });
+            return await taskCompletionSource.Task;
+        }
+
+        // There is no TaskCompletionSource<void> so we use a bool that we throw away.
+        public static async Task RunTaskAsync(this CoreDispatcher dispatcher,
+            Func<Task> func, CoreDispatcherPriority priority = CoreDispatcherPriority.Normal) =>
+            await RunTaskAsync(dispatcher, async () => { await func(); return false; }, priority);
+    }
+}