"The LINQ expression node type 'Invoke' is not supported in LINQ to Entities" - stumped!
Solution 1
You're trying to pass an arbitrary .NET function in... how could the entity framework hope to translate that into SQL? You can change it to take an Expression<Func<int, bool>>
instead, and build the Where
clause from that, although it won't be particularly easy, because you'll need to rewrite the expression with a different parameter expression (i.e. replacing whatever parameter expression is in the original expression tree with the expression of calling u.RelationTypeId
).
To be honest, for the sake of just specifying u.RelationTypeId
in the lambda expression that you use to create the expression tree to pass into the method, you'd be better off just using:
public IEnumerable<UserBandRelation> GetBandRelationsByUser(
Expression<Func<UsersBand, bool>> predicate)
{
using (var ctx = new OpenGroovesEntities())
{
var relations = ctx.UsersBands.Where(predicate);
// mapping, other stuff, back to business layer
return relations.ToList();
}
}
Solution 2
I was getting this very error and I'm using Entity Framework with PredicateBuilder by Joe Albahari to build dynamic where
clauses. If you happen to be in the same condition, you should call the AsExpandable
method:
If querying with Entity Framework, change the last line to this:
return objectContext.Products.AsExpandable().Where(predicate);
This method is part of LINQKIT DLL that you can grab here or through a NuGet package here.
Everything works fine now. :)
Solution 3
You can call the Expand()
method on your predicate
before the Where
request.
Ryan Peters
I absolutely love what I do and it is my passion. At my current position, I worked primarily using Microsoft technologies to create and maintain client-facing and internal web applications used throughout the company. All applications leveraged ASP.NET/C#, the MVC framework, WCF/ASMX/REST web services in a SOA, custom DAL wrappers, with SQL server as a storage tier. By night I'm a father of two amazing (also hectic). I also enjoy playing music and PC gaming.
Updated on July 05, 2022Comments
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Ryan Peters almost 2 years
In my EF later, I'm trying to pass in an anonymous function to be used as part of my Linq query. The function would pass in an INT and return a BOOL (u.RelationTypeId is an INT). Below is a simplified version of my function:
public IEnumerable<UserBandRelation> GetBandRelationsByUser(Func<int, bool> relation) { using (var ctx = new OpenGroovesEntities()) { Expression<Func<UsersBand, bool>> predicate = (u) => relation(u.RelationTypeId); var relations = ctx.UsersBands.Where(predicate); // mapping, other stuff, back to business layer return relations.ToList(); } }
However, I get the error stated above. It seems like I'm going everything correct by building a predicate from the function. Any ideas? Thanks.
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Ryan Peters about 13 yearsThanks. That's sort of what I thought, but my problem is that UserBandRelation is a model while UsersBand is my entity model. I use automapper to map these. Automapper has a problem if I try something crazy like mapping the expressions. Is there any way around this, in order to keep my entities separate? Thanks.
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Jon Skeet about 13 years@Ryan: As I say, you could try to go about doing expression tree rewriting. It's just not something I've tried... I also haven't used Automapper, so I'm not quite sure where that comes into it.
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Marc Gravell about 13 years@Ryan somewhere here on SO is a sample I wrote that will happen flatten
Expression.Invoke
for the purpose of allowing EF to work with sub-expressions (something L2S supports out-of-the-box). It still can't work with delegates, of course - In just saying that a rewriter is here somewhere... -
Marc Gravell about 13 years@Ryan here, in fact - just enable "inline"
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Chris Pitman about 13 years@Ryan @Marc There is also LinqKit, which incorporates many features needed for manipulating expressions.
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user483679 over 10 yearsI second Chris's suggestion of LinqKit => it makes chaining Expression<Func<YourType, bool>> predicates together extremely easy.
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haim770 over 10 years
AsEnumerable()
will cause theWhere()
function to be invoked by Linq to Objects and not Linq to Entities. -
Jonathan Wood about 10 years@JonSkeet: That's great, but I have a similar case where the property I need to evaluate is determined at run time by the user. So I tried
Expression<Func<Hotel, decimal>> getProperty = h => h.NumberOfDiamonds;
and thenquery = query.Where(h => getProperty(h) == 0)
but I get the errorgetProperty is a variable but is used like a method
. Is that possible? -
Cody about 10 yearsDo you know if
AsExpandable()
causes any performance impact? I am using a generic repository and only use the predicate builder occasionally, is it worth it to create a separate repository method for predicate building? -
Leniel Maccaferri about 10 years@Cody... I have no idea. You'd better ask that to Joe Albahary directly. :) This is his twitter: twitter.com/linqpad
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Marc over 8 years@DoctorOreo Have you figured out the performance impact? I'm in the same situation as you
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Cody over 8 years@Marc you know what, I've been using it since I guess April of 2014 and I haven't noticed any issues. Going on a year and a half now in a production application, nobody has complained. (this is a system with ~50 users dealing with anywhere from 10,000 to 5,000,000 records)
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Stephane Mathis over 8 yearsThis works too ! And I don't know what AsExpandable do, so I prefer to just call Expand when I really want to filter the query.
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Gup3rSuR4c over 6 yearsLooks like with the latest version you don't need to use
AsExpandable()
to pass in the predicate toWhere()
. Possibly because of the newPredicateBuilder.New<T>()
starting point?