如何在linq中实现更多条件包括实体 [英] how to do more conditional includes in linq to entities

问题描述

我有ac #win应用程序，我会使用linq的导航属性仅适用于某些条件。

例如我有这个类

i have a c# win application and i would use navigation properties of linq only for some conditiones are applied.
for example i have this class

public class t020
   {
       public decimal ID_CLIENTE { get; set; }
       public Nullable<decimal> ID_COMUNE { get; set; }
       public Nullable<decimal> ID_CONSORZIO { get; set; }
   }

带有此导航属性的

with this navigation properties

public partial class T232 
    {
        public decimal ID_CLIENTE_CONTO { get; set; }
        public Nullable<decimal> ID_SISTEMA { get; set; }
        public decimal ID_CLIENTE { get; set; }
     }
     public partial class T234 
    {
        public decimal ID_CONTO { get; set; }
        public decimal ID_CLIENTE { get; set; }
     }

i将使用包含T232和t234但仅应用某些条件，例如使用此变量：

字符串MyString = null

十进制MyDecimal = 8

因此我只在Mystring不为null时才使用include来使用包含t232

并且只有当mydecimal = 8才能使用包括y234

i会有这样的查询

i would use include of T232 and of t234 only some condition are applied for example using this variables:
string MyString =null
decimal MyDecimal =8
and so i would using include only when Mystring is not null to use Include of t232
and only when mydecimal =8 to use include of y234
i would have a query like this

using (var cont = DALProvider.CreateEntityContext())
{
   var result = from da in dalProv.Include(i => i.T232 where MyString!=null)
                                  .Include(i => i.T23d where MyDecimal==8)
                select da
}

等等但这样linq给了我错误。

我怎么能在linq中做到这一点？



非常感谢

and so on but in this way linq gives me error.
how can i do this in linq?

thanks a lot

推荐答案

您不能将include的条件指定为.Include（..）的参数。



而是只是有条件地执行包含：

You can't specify the condition for the include as an argument to .Include(..).

Instead just perform the include conditionally:

using (var cont = DALProvider.CreateEntityContext())
{
   var query = dalProv;

   if (MyString != null)
      query = query.Include(i => i.T232);

   if (MyDecimal == 8)
      query = query.Include(i => i.T234);

   // potentially further includes or where-predicates...
   // query = query.Where(...)

   return query;
}

确定你可以：

Well sure you can:

using (var cont = DALProvider.CreateEntityContext())
{
   var query= dalProv.Include(i => i.T232 where MyString!=null)
   if(mydecimal =8)
        query = query.Include(i => i.T23d where MyDecimal==8)

  var result = from da in query
                select da
}

这篇关于如何在linq中实现更多条件包括实体的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！