I am trying
to write some generic
LINQ queries for my entities, but am having issue doing the more complex things. Right now I am using an EntityDao class that has all my generics and each of my object class Daos (such as Accomplishments Dao) inherit it, am example:
using LCFVB.ObjectsNS;
using LCFVB.EntityNS;
namespace AccomplishmentNS
{
public class AccomplishmentDao : EntityDao<Accomplishment>{}
}
Now my entityDao has the following code:
using LCFVB.ObjectsNS;
using LCFVB.LinqDataContextNS;
namespace EntityNS
{
public abstract class EntityDao<ImplementationType> where ImplementationType : Entity
{
public ImplementationType getOneByValueOfProperty(string getProperty, object getValue)
{
ImplementationType entity = null;
if (getProperty != null && getValue != null) {
//Nhibernate Example:
//ImplementationType entity = default(ImplementationType);
//entity = Me.session.CreateCriteria(Of ImplementationType)().Add(Expression.Eq(getProperty, getValue)).UniqueResult(Of InterfaceType)()
LCFDataContext lcfdatacontext = new LCFDataContext();
//Generic
LINQ Query Here
lcfdatacontext.GetTable<ImplementationType>();
lcfdatacontext.SubmitChanges();
lcfdatacontext.Dispose();
}
return entity;
}
public bool insertRow(ImplementationType entity)
{
if (entity != null) {
//Nhibernate Example:
//Me.session.Save(entity, entity.Id)
//Me.session.Flush()
LCFDataContext lcfdatacontext = new LCFDataContext();
//Generic
LINQ Query Here
lcfdatacontext.GetTable<ImplementationType>().InsertOnSubmit(entity);
lcfdatacontext.SubmitChanges();
lcfdatacontext.Dispose();
return true;
}
else {
return false;
}
}
}
}
I have gotten the insertRow function working, however I am not even sure how
to go about doing getOnebyValueOfProperty, the closest thing I could find on this site was:
http://stackoverflow.com/questions/2157560/generic-linq-to-sql-query
How can I pass in the column name and the value I am checking against generically using my current set-up? It seems like from that link it's impossible since using a where predicate because entity class doesn't know what any of the properties are until I pass them in.
Lastly, I need some way of setting a new object as the return type set
to the implementation type, in nhibernate (what I am trying
to convert from) it was simply this line that did it:
ImplentationType entity = default(ImplentationType);
However default is an nhibernate command, how would I do this for LINQ?
EDIT:
getOne doesn't seem
to work even when just going off the base class (this is a partial class of the auto generated
LINQ classes). I even removed the generics. I tried:
namespace ObjectsNS
{
public partial class Accomplishment
{
public Accomplishment getOneByWhereClause(Expression<Action<Accomplishment, bool>> singleOrDefaultClause)
{
Accomplishment entity = new Accomplishment();
if (singleOrDefaultClause != null) {
LCFDataContext lcfdatacontext = new LCFDataContext();
//Generic
LINQ Query Here
entity = lcfdatacontext.Accomplishments.SingleOrDefault(singleOrDefaultClause);
lcfdatacontext.Dispose();
}
return entity;
}
}
}
Get the following error:
Error 1 Overload resolution failed because no accessible 'SingleOrDefault' can be called with these arguments:
Extension method 'Public Function SingleOrDefault(predicate As System.
Linq.Expressions.Expression(Of System.Func(Of Accomplishment, Boolean))) As Accomplishment' defined in 'System.
Linq.Queryable': Value of type 'System.Action(Of System.Func(Of LCFVB.ObjectsNS.Accomplishment, Boolean))' cannot be converted
to 'System.
Linq.Expressions.Expression(Of System.Func(Of LCFVB.ObjectsNS.Accomplishment, Boolean))'.
Extension method 'Public Function SingleOrDefault(predicate As System.Func(Of Accomplishment, Boolean)) As Accomplishment' defined in 'System.
Linq.Enumerable': Value of type 'System.Action(Of System.Func(Of LCFVB.ObjectsNS.Accomplishment, Boolean))' cannot be converted
to 'System.Func(Of LCFVB.ObjectsNS.Accomplishment, Boolean)'. 14 LCF
Okay no problem I changed:
public Accomplishment getOneByWhereClause(Expression<Action<Accomplishment, bool>> singleOrDefaultClause)
to:
public Accomplishment getOneByWhereClause(Expression<Func<Accomplishment, bool>> singleOrDefaultClause)
Error goes away. Alright, but now when I try
to call the method via:
Accomplishment accomplishment = new Accomplishment();
var result = accomplishment.getOneByWhereClause(x=>x.Id = 4)
It doesn't work it says x is not declared.
I also tried getOne, and various other Expression
=(
