Nhibernate 加入另一个表

Question

我需要对客户执行连接。其中地址是主要地址并填充 PrimaryAddress1 和 PrimaryCity 字段。客户映射已经与地址类有很多关系，但我不想获取所有地址(性能问题)。

请帮忙..

类:

public class Customer
{
    public Customer()
    {
        Addressess = new List<Address>();
    }
   public virtual int CustomerID { get; set; }
    public virtual int? BranchID { get; set; }
    public virtual int? CustTypeID { get; set; }
    public virtual string CompanyName { get; set; }
    public virtual string Prefix { get; set; }
    public virtual string FirstName { get; set; }
    public virtual string MiddleName { get; set; }
    public virtual string LastName { get; set; }
    public virtual string PrimaryAddress1 { get; set; }
    public virtual string PrimaryCity { get; set; }
    public virtual List<Address> Addresses { get; set; }
}


public class Address
{
    public Address()
    {
    }
    public virtual int LocationID { get; set; }
    public virtual int? CustomerID { get; set; }
    public virtual string LocationName { get; set; }
    public virtual string Address1 { get; set; }
    public virtual string Address2 { get; set; }
    public virtual string Address3 { get; set; }
    public virtual string City { get; set; }
    public virtual bool Primary { get; set; }
}

映射:

public TblCustomerMap()
{
    Table("tblCustomers");
    LazyLoad();
    Id(x => x.CustomerID).GeneratedBy.Identity().Column("CustomerID");
    Map(x => x.ProfileID).Column("ProfileID");
    Map(x => x.BranchID).Column("BranchID");
    Map(x => x.DateEntered).Column("DateEntered");
    Map(x => x.DateTerminated).Column("DateTerminated");
    Map(x => x.CustTypeID).Column("CustTypeID");
    Map(x => x.CompanyName).Column("CompanyName").Not.Nullable().Length(50);
    Map(x => x.Prefix).Column("Prefix").Not.Nullable().Length(50);
    Map(x => x.FirstName).Column("FirstName").Not.Nullable().Length(50);
    Map(x => x.MiddleName).Column("MiddleName").Not.Nullable().Length(50);
    Map(x => x.LastName).Column("LastName").Not.Nullable().Length(50);
    HasMany(x => x.Address).KeyColumn("CustomerID");
    Map(x => x.PrimaryAddress1).Column("PrimaryAddress1") // from table tbladdress where address is primary and get data from address1 column
    Map(x => x.PrimaryCity).Column("PrimaryCity") // from table tbladdress where address is primary and get data from city column
}

查询:

 var query = session
            .QueryOver<Customer>(() => customer)
            .JoinQueryOver(() => customer.Addresses, () => address)
            .Where(() => address.Primary)
            .List();

        foreach (var customer1 in query)
        {
            customer1.PrimaryAddress1 = customer1.Addresses[0].Address1;
            customer1.PrimaryCity = customer1.Addresses[0].City;
            customer1.PrimaryState = customer1.Addresses[0].StateOrProvince;

        }

新查询:

  var query = session.Query<Customer>()
            .SelectMany(c => c.Addresses,
                        (c, a) => new {c, a})
            .Where(cust => cust.a.Primary)
            .Select(item => new CustomerView()
                              {
                                 CustomerID = item.c.CustomerID,
                                 CompanyName=  item.c.CompanyName,
                                 FirstName=  item.c.FirstName,
                                  LastName=item.c.LastName,
                                  Address1=item.a.Address1,
                                  Address2=item.a.Address2,
                                 Address3= item.a.Address3,
                                 City= item.a.City,
                                 StateOrProvince= item.a.StateOrProvince
                              });
        return query.ToList();

Answer 1

有(至少)两种方法可以实现这一目标。

1) 更直观和可读的是扩展数据库和调整NHibernate 映射。我们需要创建新的view viewPrimaryAddress。

SELECT ***columns*** FROM [tbladdress] WHERE Primary = true

客户映射将如下所示:

Join("[viewPrimaryAddress]", 
{
  m.Fetch.Join();
  m.KeyColumn("CustomerID");
  m.Map(t => t.PrimaryAddress1).Column("PrimaryAddress1");
  m.Map(t => t.PrimaryCity).Column("PrimaryCity");
});

就是这样。会发出一条SQL语句，所以不需要加载Address集合

2) 第二种方法的概述

第二种方法将通过新类映射创建该 View ，有点复杂，但只能在应用程序端(C# 和 NHiberante)完成。

将创建新类 PrimaryAddress 并在类级别定义中包含过滤器(xml 映射示例:

<class name="PrimaryAddress" ... where="Primary = true" >

然后我们可以使用与 PrimaryAddress 的新多对一 关系来扩展 Customer。因此，获取列“PrimaryAddress1”和“PrimaryCity”的属性将通过在 WHERE 子句中过滤的 SQL 选择来完成。

扩展:

接下来的步骤应该指导您如何创建新映射，将主地址作为一对一属性1) C# 主地址:

public class PrimaryAddress
{
    public virtual Customer Customer { get; set; }
    public virtual string Address { get; set; }
    public virtual string City { get; set; }
}

2)映射:

public TblPrimaryAddressMap()
{
    Table("tbladdress");
    LazyLoad();
    Where("Primary = 1");
    // Id as AddressId
    References(x => x.Customer).Column("CustomerID");
    Map(x => x.Address).Column("PrimaryAddress1")
    Map(x => x.PrimaryCity).Column("PrimaryCity")
}

3) Customer 的新属性

public class Customer
{  
   ..
   public virtual PrimaryAddress PrimaryAddress { get; set; }

4) Customer 的新映射公共(public) TblCustomerMap(){ ... HasOne(x => x.PrimaryAddress)

此时，当您从 session 中获取Customer 时。您可以访问

customer.PrimaryAddress.Address
customer.PrimaryAddress.City

我主要使用 XML 映射。但是从这些行来看，概念应该很清楚......玩一些 fetch="join" 你可以加载 Customer 和它的 PrimaryAddress 在一个SQL 选择

如果您甚至需要客户属性 Customer.PrimaryAddress1，只需将 PrimaryAddress.Address 包装在 getter 中即可。

您将获得更多的好处是可以通过这个新属性 PrimaryAddress

进行过滤和排序

注意:这种方法对于缓存来说是脆弱的。原因是，虽然您将更改真实的 Address 实体，但没有内置机制来驱逐 PrimaryAddress。而且，您应该强制业务层只允许一个地址设置为 primary = true 的客户