Enitity Framework primary key and ForeignKey delete

protected override void OnModelCreating(DbModelBuilder modelBuilder)
       {


       modelBuilder.Entity<EmailCampaignCustomize>().HasRequired(m => m.EmailCampaign).WithMany(m => m.EmailCampaignCustomize).WillCascadeOnDelete(true);


           modelBuilder.Entity<EmailCampaignCustomize>().HasRequired(m => m.EmailCampaign).WithMany(m => m.EmailCampaignCustomize).HasForeignKey(m => m.EmailCampaignId).WillCascadeOnDelete(true);
           base.OnModelCreating(modelBuilder);
       }