查詢與Linq的多對多關系

Question

我有一個名為CustomerGroup的表，該表與表contact_List有許多關系。 第三個表CustomerGroupContact具有兩個表的主鍵。

這是CustomerGroup表的外觀：

public class CustomerGroup
{
    public CustomerGroup()
    {
        CustomerGroupContacts = new HashSet<CustomerGroupContact>();

    }

    [Key]
    public int Customer_Group_Code { get; set; }

    public int Customer_Code { get; set; }

    public string Customer_Group_Name { get; set; }


    public virtual ICollection<CustomerGroupContact> CustomerGroupContacts { get; set; }

}

這是Contact_List模型的樣子：

public class Contact_List
{
    [Key]
    public int Contact_List_Code { get; set; }

    public int Customer_Code { get; set; }

    public string First_Name { get; set; }

    public string Last_Name { get; set; }

    public string Contact_No { get; set; }

}

我正在嘗試加入2個表來創建一個對象，該對象看起來像下面的模型：

    public class Contacts
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string ContactNo { get; set; }
    public string GroupName { get; set; }
}

我正在努力使用正確的查詢語句，該語句將基於customer_code屬性加入表。 我將不勝感激。

Answer 1

嘗試以下操作：

            List<CustomerGroup> groups = new List<CustomerGroup>();
            List<Contact_List> contact_list = new List<Contact_List>();

            List<Contacts> contacts = (from g in groups
                                       join c in contact_list on g.Customer_Code equals c.Customer_Code
                                       select new { groupName = g.Customer_Group_Name, c })
                                       .Select(x => new Contacts() {
                                           FirstName = x.c.First_Name,
                                           LastName = x.c.Last_Name,
                                           ContactNo = x.c.Contact_No,
                                           GroupName = x.groupName
                                       }).ToList();

Answer 2

這行得通嗎？

private IEnumerable<Contacts> JoinTables(IEnumerable<Contact_List> contactLists, IEnumerable<CustomerGroup> customerGroups)
{    
    return contactLists.Join(customerGroups, 
                             x => x.Customer_Code, 
                             y => y.Customer_Code, 
                             (x, y) => new Contacts()
                             {
                                ContactNo = x.Contact_No,
                                FirstName = x.First_Name,
                                LastName = x.Last_Name,
                                GroupName = y.Customer_Group_Name
                             });
}

Answer 3

希望這會起作用：

    var userContactList = (from custGroup in _db.CustomerGroup
                           join     cList in _db.Contact_List 
                           on custGroup.Customer_Code equals cList.Customer_Code
                           select new Contacts {
                                            FirstName = cList.First_Name,
                                            LastName = cList.Last_Name,
                                            ContactNo = cList.Contact_No, 
                                            GroupName = custGroup.Customer_Group_Name
                                            }).ToList();