OnModelCreatingNoGen.cs

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Blog>().Property(x => x.Id).ValueGeneratedNever();
    modelBuilder.Entity<Blog>().HasKey(x => x.Id);
    modelBuilder.Entity<Blog>().HasMany(x=>x.Posts).WithOne().IsRequired();
    modelBuilder.Entity<Blog>().Property(x => x.Name);

    modelBuilder.Entity<Post>().Property(x => x.Id).ValueGeneratedNever();
    modelBuilder.Entity<Post>().HasKey(x => x.Id);
    modelBuilder.Entity<Post>().Property(x => x.Title);
    modelBuilder.Entity<Post>().Property(x => x.Content);

    base.OnModelCreating(modelBuilder);
}