how to do more conditional includes in linq to entities

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C#

LINQ

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; }
   }

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 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
}

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

thanks a lot