Migrate to Avalonia (#1220)

DiscordChatExporter.Gui/Converters/LocaleToDisplayNameStringConverter.cs

@@ -0,0 +1,22 @@
+using System;
+using System.Globalization;
+using Avalonia.Data.Converters;
+
+namespace DiscordChatExporter.Gui.Converters;
+
+public class LocaleToDisplayNameStringConverter : IValueConverter
+{
+    public static LocaleToDisplayNameStringConverter Instance { get; } = new();
+
+    public object Convert(object? value, Type targetType, object? parameter, CultureInfo culture) =>
+        value is string locale && !string.IsNullOrWhiteSpace(locale)
+            ? CultureInfo.GetCultureInfo(locale).DisplayName
+            : "System default";
+
+    public object ConvertBack(
+        object? value,
+        Type targetType,
+        object? parameter,
+        CultureInfo culture
+    ) => throw new NotSupportedException();
+}