sandbox-aspnet-mvc-tempdata-enum

• .NET Core 3.1.x
• ASP.NET 3.1.23

Steps to reproduce

Click "OK" link.

• Set State=OK and redirect to Index page
• Show State=OK (Cookies should be deleted here, but they are not.)

Click "Reload" link. (or F5)

• Expect: State=VIEW
• Actual: State=OK

Why undelete enum value on TempData?

The code here does not take enum into account.

https://github.com/dotnet/aspnetcore/blob/v3.1.23/src/Mvc/Mvc.ViewFeatures/src/Filters/SaveTempDataPropertyFilterBase.cs#L55

OriginalValue derived from Cookie is handled as int, but newValue is handled as Enum since it is derived from Property.

See Variables in the following debugger for type differences

eg.) string Message

eg.) enum State

Therefore, newValue.Equals(OriginalValue) becomes (1.Equals((Enum)1) and returns false. Then tempData[key] = newValue is processed and tempData._initialKeys is set, thus creating a cookie.