如何制作不同实体类的对象并在数据库MVC4中存储记录

这是我的控制器方法。它返回空值。任何建议。

[HttpPost]
public ActionResult CreatBranch()
{
    if (ModelState.IsValid)
    {
            var contactinfo = new ContactInfo();
            db.ContactInfo.Add(contactinfo);
            db.SaveChanges();
            var contctid = contactinfo.ContactID;
            var addressinfo = new Address();
            db.Address.Add(addressinfo);
            db.SaveChanges();
            var addid = contactinfo.ContactID;
            var branchInfo = new Branch { ContactID = contctid, AddressID = addid, CreatedDate = DateTime.Now, CreatedBy = Convert.ToInt32(Session["UserID"]), UpdatedBy = Convert.ToInt32(Session["UserID"]) , UpdatedDate = DateTime.Now};
            db.Branches.Add(branchInfo);
            db.SaveChanges();
            return RedirectToAction("Index");
    }
    return RedirectToAction("Index");
}
//int contact id returns int value, int add also returns an int value. but remaining attributes are passing null values .