Nullable exception after updating to Preview-8 (Nullable object must have a value)

In case of move to last version of ef core (5.0.0-preview.8.20407.4), app throws exceptions: “nullable object must have value” for all objects that contains some nullable defined member…

All older versions works only prev-8 not… ( tested on prev 5,6,7 as OK )

• Tested with different DBs (SQL/SQLite/Postgres) (So i think it is not provider related…)
• Tested that this is not migration or tools related…

This happens when any object has some Nullable member which is null… Im adding example for UserRole Null…

Example DB model:

 public class User {

        public long ID { get; set; }

        public string UserName {
            get {
                return String.Format("{0}.{1}", FirstName, LastName);
            }
        }

#nullable enable
        public string? AvatarFileName { get; set; }
#nullable disable

        public string FirstName { get; set; }

        public string LastName { get; set; }

#nullable enable
        public string? Email { get; set; }
#nullable disable

        public User() {
            this.Tokens = new HashSet<RefreshToken>();
            this.Groups = new HashSet<GroupUser>();
            this.Claims = new HashSet<UserPermission>();
            this.Email = "";
            this.AvatarFileName = "";
        }

#nullable enable
        public DateTime? ActivTimestamp { get; set; }
#nullable disable

        public bool Deactivated { get; set; }

        virtual public IEnumerable<RefreshToken> Tokens { get; set; }

#nullable enable
        virtual public Role? Role { get; set; }
#nullable disable

        virtual public IEnumerable<GroupUser> Groups { get; set; }
....
   ....
     etc.
    }

From SELECT:

SELECT "t"."ID", "t"."Email", "t"."FirstName", "t"."LastName", "r"."ID", "r"."Name", "r"."Description", "r"."Code", "t"."ActivTimestamp", "t"."AvatarFileName" AS "AvatarImageName", "t"."Deactivated"
FROM (
    SELECT "u"."ID", "u"."ActivTimestamp", "u"."AvatarFileName", "u"."Deactivated", "u"."Email", "u"."FirstName", "u"."LastName", "u"."RoleID"
    FROM "Users" AS "u"
    WHERE ("u"."FirstName" IS NOT NULL AND NOT ("u"."Deactivated")) OR ("u"."LastName" IS NOT NULL AND NOT ("u"."Deactivated"))
    LIMIT @__p_0
) AS "t"
LEFT JOIN "Roles" AS "r" ON "t"."RoleID" = "r"."ID"

Throw:

 An exception occurred while iterating over the results of a query for context type 'Presistence.AppDbContext'.
System.InvalidOperationException: Nullable object must have a value.
   at lambda_method(Closure , QueryContext , DbDataReader , ResultContext , SingleQueryResultCoordinator )
   at Microsoft.EntityFrameworkCore.Query.Internal.SingleQueryingEnumerable`1.AsyncEnumerator.MoveNextAsync()
System.InvalidOperationException: Nullable object must have a value.
   at lambda_method(Closure , QueryContext , DbDataReader , ResultContext , SingleQueryResultCoordinator )
   at Microsoft.EntityFrameworkCore.Query.Internal.SingleQueryingEnumerable`1.AsyncEnumerator.MoveNextAsync()
System.InvalidOperationException: Nullable object must have a value.
   at lambda_method(Closure , QueryContext , DbDataReader , ResultContext , SingleQueryResultCoordinator )
...
  ...
   etc.

Versions: EF Core version: 5.0.0-preview.8.20407.4 Database provider: SqlServer or SQL or PosgreSQL (tested with all so i think it is not provider related…)

[smitpatel]

List<User_DTO> db_enity = await _context.Users.AsNoTracking()
            .Include(e=>e.Role)
            .Select(e=> new User_DTO(){
                ID = e.ID,
                Role =  e.Role == null ? null : new Role_DTO {
                ID = e.Role.ID,
                Name = e.Role.Name,
            },
            }).ToListAsync();

You need to check for e.Role being null then returning null rather than create the Role_DTO.

[damikun]

@smitpatel thx for info… Oh yes i see… So whats the workaround for this? or better say how to do this select with new prev8 ? i saw the merge is new and something going back to .net core 2.2 behavior…

For test when i change in Role_DTO public long? ID { get; set; } as nullable it will work but is this the way of handle ? To have all iDs as nullable in all DTOs ? thx