C# 9 Cleanup (#325)

- [X] Removes EventArgs - not needed
- [X] Merges sequential checks
- [X] Removes redundant type declarations

Projects/UOContent/Commands/Generic/Extensions/DistinctExtension.cs

@@ -6,7 +6,7 @@ namespace Server.Commands.Generic
     public sealed class DistinctExtension : BaseExtension
     {
         public static ExtensionInfo ExtInfo =
-            new ExtensionInfo(30, "Distinct", -1, () => new DistinctExtension());
+            new(30, "Distinct", -1, () => new DistinctExtension());
 
         private readonly List<Property> m_Properties;