How do I use func in Linq to Entity select?

Question

I want a usage like the following, but it gives error if I don't use AsEnumerable. Why I want it because I'm going to need it in many places.

Is there another way to do this?

public static class EntityHelper
{
    public static Func<TABLE1, TABLE2, TABLE2, string> SelectTitle = (trn, acc, parentAcc) => trn.master_id != trn.parent_id ? parentAcc.name : acc.name;
}

 var query = from trn in context.TABLE1
      join acc in context.TABLE2 on trn.acc_id equals acc.id
      join parentAcc in context.TABLE2 on trn.parent_id equals parentAcc.id                            
      select new {name = EntityHelper.SelectTitle.Invoke(trn,acc,parentAcc)};

System.NotSupportedException: 'LINQ to Entities does not recognize the method 'System.String Invoke(TABLE1, TABLE2,TABLE2)' method, and this method cannot be translated into a store expression.'

Answer 1

I solved this work using LinqKit nuget. I changed my code as follows.

public static class EntityHelper
{
     public static Expression<Func<TABLE1, TABLE2, TABLE2, string>> SelectTitle = (trn, acc, parentAcc) => trn.master_id != trn.parent_id ? parentAcc.name : acc.name;
}

 var query = from trn in context.TABLE1.AsExpandableEF()
      join acc in context.TABLE2 on trn.acc_id equals acc.id
      join parentAcc in context.TABLE2 on trn.parent_id equals parentAcc.id                            
      select new {name = EntityHelper.SelectTitle.Invoke(trn,acc,parentAcc)};