The migration '20201221040826_AddBlogCreatedTimestamp' has already been applied to the database. Revert it and try again. If the migration has been applied to other databases, consider reverting its changes using a new migration. code example
Example: The migration '20200806160941_InitialMigration' has already been applied to the database. Revert it and try again. If the migration has been applied to other databases, consider reverting its changes using a new migration.
dotnet ef database update 0
dotnet ef migrations remove