update

TimetableDesigner.Customs/JsonSerializableDictionary.cs

@@ -0,0 +1,14 @@
+using Newtonsoft.Json;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace TimetableDesigner.Customs
+{
+    [JsonArray]
+    public class JsonSerializableDictionary<TKey, TValue> : Dictionary<TKey, TValue> where TKey : notnull
+    {
+    }
+}

TimetableDesigner.Customs/TimetableDesigner.Customs.csproj

@@ -6,4 +6,8 @@
     <Nullable>enable</Nullable>
   </PropertyGroup>
 
+  <ItemGroup>
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
+  </ItemGroup>
+
 </Project>