返回IQueryable<;T>;来自另一个类实例
本文关键字:另一个 实例 IQueryable lt 返回 gt | 更新日期: 2023-09-27 18:29:23
我试图实现的是创建一个返回通用IQueryable<T>
的基类,并使用另一个类实例中的IQueryable
进行进一步筛选。Es。基类返回所有记录,调用类从此开始过滤
这是基类,getDealer_query是返回主IQueryable
的方法
public class Dealer
{
public DAL.DBConn_Nav db = null;
public G4.Elements.Identity oIdentity = null;
public Dealer()
{
oIdentity = new G4.Elements.Identity();
oIdentity.read();
}
public IQueryable<outerViewModel.NavisionDAL.vmDealer> getDealer_query()
{
IQueryable<vmDealer> dealer = (from d in db.DENTALICA_S_P_A__Customer
select new vmDealer()
{
idDealer = d.No_,
name = d.Name + (d.Name_2.Length > 0 ? " " + d.Name_2 : ""),
address = d.Address + (d.Address_2.Length > 0 ? " " + d.Address_2 : ""),
city = d.City,
zip = d.Post_Code,
county = d.County,
email = d.E_Mail,
phone = d.Phone_No_,
fax = d.Fax_No_,
vat = d.VAT_Registration_No_,
ssn = d.Fiscal_Code,
businessAreaCode = d.Business_Area_Code,
businessZoneCode = d.Business_Zone_Code,
clienteDiretto = (d.Cliente_Diretto == (byte)1 ? true : false),
aggancioOrdiniWeb = (d.Deposito_Agg__Ordini_Web == (byte)1 ? true : false),
aggancioOrdiniG4 = (d.Deposito_Agg__Ordini_G4 == (byte)1 ? true : false),
notUse = (d.Not_Use == (byte)1 ? true : false),
blocked = d.Blocked,
shipmentMethodCode = d.Shipment_Method_Code,
paymentTermsCode = d.Payment_Terms_Code,
paymentMethodCode = d.Payment_Method_Code,
shippingAgentCode = d.Shipping_Agent_Code,
customerPriceGroup = d.Customer_Price_Group,
customerDiscountGroup = d.Customer_Disc__Group,
identificaCliente = d.Identifica_Cliente
});
return dealer;
}
这是另一个类Customer
,它从Dealer
的实例调用方法,并最终列出数据。
public class Customer
{
G4.Elements.Identity oIdentity = null;
DAL.DBConn_Nav navDB = null;
public Customer()
{
//oIdentity = new G4.Elements.Identity();
//oIdentity.read();
}
///// <summary>
///// Recupera l'elenco dei clienti Navision (i Depositi pr G4) visibili ad un particolare utente
///// </summary>
///// <returns></returns>
public IQueryable<outerViewModel.NavisionDAL.vmDealer> getCustomerForOperator_query()
{
string idOperator = !string.IsNullOrEmpty(oIdentity.selectedId) ? oIdentity.selectedId : oIdentity.id;
using (navDB = new DAL.DBConn_Nav()) {
G4.Models.NavisionDAL.Dealer oD = new G4.Models.NavisionDAL.Dealer();
// Tutti i Clienti
IQueryable<outerViewModel.NavisionDAL.vmDealer> allCustomerList_query = oD.getDealer_query();
IQueryable<outerViewModel.NavisionDAL.vmDealer> customerForOperator_query = (from c in allCustomerList_query join cForOp in navDB.DENTALICA_S_P_A__SalesPerson_Customer on c.idDealer equals cForOp.Customer_No_
where cForOp.Salesperson_Code.Equals(idOperator)
&& cForOp.Starting_Date < DateTime.Now
&& (cForOp.Ending_Date.Equals(new DateTime(1753, 1, 1)) || cForOp.Ending_Date > DateTime.Now)
&& c.notUse.Equals(false)
select c).Distinct();
return customerForOperator_query;
}
}
public List<G4.outerViewModel.NavisionDAL.vmDealer> getCustomerForOperator()
{
using (navDB = new DAL.DBConn_Nav())
{
G4.Models.NavisionDAL.Dealer oD = new G4.Models.NavisionDAL.Dealer();
return getCustomerForOperator_query().ToList();
}
}
但它不起作用!我得到一个通用的"Object not set to a instance…"。
即使我尝试调试,我也不会得到任何结果,因为光标不会停止。
为了让它发挥作用,我必须从客户那里继承Dealer类,但这不是我想要的。
我想我错过了一些基本的东西。
有什么想法吗?
编辑-简化示例我正在添加相同代码的简化示例。
public class Dealer1
{
public DAL.DBConn_Nav db = null;
public Dealer1() {
}
public IQueryable<outerViewModel.NavisionDAL.vmDealer> getDealer_query()
{
IQueryable<vmDealer> dealer = (from d in db.DENTALICA_S_P_A__Customer
select new vmDealer()
{
idDealer = d.No_,
name = d.Name + (d.Name_2.Length > 0 ? " " + d.Name_2 : "")
});
return dealer;
}
}
public class Customer1
{
public DAL.DBConn_Nav db = null;
public Customer1()
{
}
public IQueryable<outerViewModel.NavisionDAL.vmDealer> getCustomerForOperator_query()
{
// All customers
G4.Models.NavisionDAL.Dealer1 oD = new G4.Models.NavisionDAL.Dealer1();
IQueryable<outerViewModel.NavisionDAL.vmDealer> allCustomerList_query = oD.getDealer_query().Where(i => i.name.StartsWith("AAA"));
return allCustomerList_query;
}
public List<G4.outerViewModel.NavisionDAL.vmDealer> getCustomerForOperator()
{
using (db = new DAL.DBConn_Nav())
{
return getCustomerForOperator_query().ToList();
}
}
}
类Dealer
中没有设置db
实例的内容。
public DAL.DBConn_Nav db = null;
因此,即使在Customer
中调用using (navDB = new DAL.DBConn_Nav())
,也不会将navDB
传递给Dealer
,因此当调用getDealer_query()
时,会得到一个空引用异常。
基于您的简化示例,我建议使用以下代码:
public class Dealer1
{
internal IQueryable<vmDealer> getDealer_query(DAL.DBConn_Nav db)
{
return
from d in db.DENTALICA_S_P_A__Customer
select new vmDealer()
{
idDealer = d.No_,
name = String.Join(" ", d.Name, d.Name_2)
};
}
}
public class Customer1
{
internal IQueryable<vmDealer> getCustomerForOperator_query(DAL.DBConn_Nav db)
{
return new Dealer1().getDealer_query(db).Where(i => i.name.StartsWith("AAA"));
}
public List<vmDealer> getCustomerForOperator()
{
using (var db = new DAL.DBConn_Nav())
{
return getCustomerForOperator_query(db).ToList();
}
}
}
这可以干净地隔离责任,但它可以让您完全控制db
实例——完成后需要处理它。
allCustomerList_query
为空应该没有任何原因。
为了确认getDealer_query
方法中的linq语句正在工作,我会将您的代码更改为:
List<outerViewModel.NavisionDAL.vmDealer> something = new List<outerViewModel.NavisionDAL.vmDealer>();
IQueryable<outerViewModel.NavisionDAL.vmDealer> test = something.AsQueryable();
return test;
在任何情况下,为了防止对象引用错误,您需要保证返回一个实例,从代码示例中,我实际上无法判断。
奇怪的是,在getDealer_query
方法中无法获得停止的断点。你是在多个线程运行的测试中运行这个吗?可能发生的情况是,另一个线程引发了未处理的异常,因此整个测试停止。尝试在getDealer_query
的return dealer
之前和G4.Models.NavisionDAL.Dealer oD = new G4.Models.NavisionDAL.Dealer();
线上放置断点。假设没有其他线程,代码必须在其中一个线程上停止。
最后要注意的是,查看代码,我看不出db
在哪里实例化。如果它没有被实例化,你会在这行得到一个对象引用错误:
`IQueryable<vmDealer> dealer = (from d in db.DENTALICA_S_P_A__Customer`