sorry, i was wrong this time... let me help to clarify what i did to get it
working on linqspecs:
Previously i had this code, and it doesn't work with nhibernate 3 linq
provider:
ParameterExpression·param·=·Expression.Parameter(typeof(T),·"x");
Expression.Lambda<Func<T,·bool>>(
Expression.AndAlso(
Expression.Invoke(expr1,·param),
Expression.Invoke(expr2,·param)),·param);
So, with the help of Fabio we changed to this:
ParameterExpression param = expr1.Parameters[0];if
(ReferenceEquals(param, expr2.Parameters[0]))
{
// simple version
return Expression.Lambda<Func<T,
bool>>(Expression.AndAlso(expr1.Body, expr2.Body), param);
}// otherwise, keep expr1 "as is" and invoke expr2return
Expression.Lambda<Func<T, bool>>(Expression.AndAlso(expr1.Body,
Expression.Invoke(expr2, param)), param);
This do works with nh3 linq provider.
I don't get the difference yet
2011/1/7 José F. Romaniello <[email protected]>
> You are wrong, and you should avoid Expression.Invoke, my linq spec project
> does exactly this, and it works.
> http://linqspecs.codeplex.com/
>
> <http://linqspecs.codeplex.com/>given expr1 and expr2, you can always do
> this:
>
> ParameterExpression param = expr1.Parameters[0];if (ReferenceEquals(param,
> expr2.Parameters[0]))
> {
> return Expression.Lambda<Func<T, bool>>(Expression.AndAlso(expr1.Body,
> expr2.Body), param);
> }return Expression.Lambda<Func<T, bool>>(Expression.AndAlso(expr1.Body,
> Expression.Invoke(expr2, param)), param);
>
>
> See my AndSpecification here:
>
>
> http://linqspecs.codeplex.com/SourceControl/changeset/view/f8b332648229#LinqSpecs%2fAndSpecification.cs
>
>
> <http://linqspecs.codeplex.com/SourceControl/changeset/view/f8b332648229#LinqSpecs%2fAndSpecification.cs>
> 2011/1/7 Fabian Schmied <[email protected]>
>
> Hi,
>>
>> PredicateBuilder uses a neat little trick that is, however, not supported
>> by NHibernate yet: to fit a LambdaExpression in a place where no
>> LambdaExpression is allowed, it builds an InvocationExpression around the
>> LambdaExpression. NHibernate does not evaluate that InvocationExpression.
>>
>> I've opened a JIRA issue to solve this at the re-linq level because this
>> is something all LINQ providers based on re-linq (not only NHibernate) would
>> benefit from: https://www.re-motion.org/jira/browse/RM-3656.
>> I can't promise anything, but I'm planning to implement a few new
>> features for re-linq this January, so this might be working soon in re-linq
>> - and, after they take over the latest re-linq version, in NHibernate as
>> well.
>>
>> In the meantime, you could use a modified version of PredicateBuilder
>> (modified from http://www.albahari.com/nutshell/predicatebuilder.aspx):
>>
>> public static Expression<Func<T, bool>> And<T> (this Expression<Func<T,
>> bool>> expr1,
>> Expression<Func<T,
>> bool>> expr2)
>> {
>> var adaptedExpr2Body = ReplacingExpressionTreeVisitor.Replace
>> (expr2.Parameters.Single(), expr1.Parameters.Single(), expr2.Body);
>> return Expression.Lambda<Func<T, bool>>
>> (Expression.AndAlso (expr1.Body, adaptedExpr2Body),
>> expr1.Parameters);
>> }
>>
>> (Untested, from my head. ReplacingExpressionTreeVisitor is a part of
>> re-linq and resides in the Remotion.Data.Linq.Parsing,ExpressionTreeVisitors
>> namespace.)
>> "Or" would need to be adapted in a similar fashion.
>>
>> Hope this helps,
>> Fabian
>>
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