Entity Framework Core code first default values for PostgreSQL

As the EF Core docs mention, HasDefaultValue() and HasDefaultValueSql() only specify the value that gets set when a new row is inserted. Setting a column to null is a completely different thing (after all, null is a valid value for those columns). You may be looking for computed columns, which is a different feature.

Unfortunately, as the Npgsql docs mention, computed columns aren't supported by PostgreSQL at this time. It's possible to set this up using PostgreSQL database triggers, but this isn't managed by EF Core so you'd have to use SQL in your migrations to set this up.

Solution for CreateDate in PostgreSQL:

builder.Property(e => e.CreationDate)
  .HasColumnType("timestamp without time zone")
  .HasDefaultValueSql("NOW()")
  .ValueGeneratedOnAdd();

Unfortunately there is not solution for update event.