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I'm using LINQKit to expand LINQ To Entities capabilities: 

public Boolean IsMatched(Int32 age)
{
    return age > 18;
}

public IQueryable<Users> GetAllMatchedUsers(Func<Int32, Boolean> isMatched)
{
    return qry = _Context.Users.AsExpandable().Where(x => x.IsActive && isMatched(x.Age));
}

This code is used for Entity Framework ORM objects (_Context is DbContext, Users - is DBSet)

This code throws following exception

Unable to cast object of type 'System.Linq.Expressions.FieldExpression' to type 'System.Linq.Expressions.LambdaExpression'

Getting rid of Func and hardcoding IsMatched into GetAllMatchedUsers solves this problem. But I need to use Func to pass different selection criteria from Business Logic Layer to my Data Access Layer

P. S. IsMatched is highly simplified realisation for example of course

Help me please.

bairog
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  • Are you also missing a parameter name in your code or is it just here? – Ondrej Janacek Oct 25 '13 at 11:59
  • Just here :) I've corrected my code sample.. – bairog Oct 25 '13 at 15:11
  • Added some more info about what is _Context and Users are – bairog Oct 25 '13 at 15:28
  • Why do you use that `AsExpandable`? It seems redundant to me. Why the `Where` clause is not enough? – Ondrej Janacek Oct 25 '13 at 16:16
  • AsExpandable is LINQKit extention method. Without it enother exception is raised which tells me that LINQ to Entities doesn't suppert Invoke. I've expected AsExpandable to solve this problem (as far as I understanded LINQKit documentation) - but I've failed and described my code here... – bairog Oct 27 '13 at 06:49

1 Answers1

1

With LinqKit you'll have to pass Expression<Func<Int32, Boolean>> isMatched

Func<...> is something that is compiled already to C# runtime.

Expression<Func<...>> is something that you can transfer as expression tree to SQL.

Tuomas Hietanen
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