Migrate to Avalonia (#1220)

DiscordChatExporter.Gui/Converters/SnowflakeToTimestampStringConverter.cs

@@ -0,0 +1,25 @@
+using System;
+using System.Globalization;
+using Avalonia.Data.Converters;
+using DiscordChatExporter.Core.Discord;
+
+namespace DiscordChatExporter.Gui.Converters;
+
+public class SnowflakeToTimestampStringConverter : IValueConverter
+{
+    public static SnowflakeToTimestampStringConverter Instance { get; } = new();
+
+    public object? Convert(
+        object? value,
+        Type targetType,
+        object? parameter,
+        CultureInfo culture
+    ) => value is Snowflake snowflake ? snowflake.ToDate().ToString("g", culture) : null;
+
+    public object ConvertBack(
+        object? value,
+        Type targetType,
+        object? parameter,
+        CultureInfo culture
+    ) => throw new NotSupportedException();
+}