LINQ to Entities does not recognize the method 'System.String ToBase64String(Byte[])' method,

Question

LINQ to Entities does not recognize the method 'System.String ToBase64String(Byte[])' method, and this method cannot be translated into a store expression.

 var activityList = (from item in committeeMemberList
                let committee = db.Committee.FirstOrDefault(x => x.Committee_Id == item.Committee_Id)
                let contact = db.Contacts.FirstOrDefault(x => x.Contact_Id == item.Contact_Id)
                select new Activity
                {
                   Id = Convert.ToBase64String(item.Committee_Member_SPE_Id), 
                   Name = committee.Committee_Name, 
                   ...
                   ...

                  }).ToList();

you have to do conversion after LINQ. I had such problem ( i couldn't convert ID to integer during linq query ) And i converted it later in code. — Adrian Księżarczyk, Mar 13 '13 at 17:38
The problem is that the function `ToBase64String` can't be compiled to SQL. When `ToList()` is called, query is built, and the list is filled. This means you have to call `ToList()` before you call the function`ToBase64String`. — Peter Bruins, Apr 10 '17 at 12:58

score 3 · Accepted Answer · answered Mar 13 '13 at 17:39

Change your LINQ so that your original statement returns a list of anonymous objects, and then select on THAT list and use the ToBase64String function:

var activityList = 
            (from item in
                (from member in committeeMemberList
                let committee = db.Committee.FirstOrDefault(x => x.Committee_Id == item.Committee_Id)
                let contact = db.Contacts.FirstOrDefault(x => x.Contact_Id == item.Contact_Id)
                select new
                {
                   Id = member.Committee_Member_SPE_Id, 
                   Name = committee.Committee_Name, 
                   ...
                   ...
                 }).ToList())
            select new Activity
            {
               Id = Convert.ToBase64String(item.Id), 
               Name = committee.Committee_Name, 
               ...
               ...

            }).ToList();

(apparently this did work because it was the accepted answer) — scott.korin, Dec 20 '18 at 19:54

score 0 · Answer 2 · answered Apr 10 '17 at 12:54

    var activityList = 
                (from item in
                    (from member in committeeMemberList
                    let committee = db.Committee.FirstOrDefault(x => x.Committee_Id == item.Committee_Id)
                    let contact = db.Contacts.FirstOrDefault(x => x.Contact_Id == item.Contact_Id)
                    select new
                    {
                       Id = member.Committee_Member_SPE_Id, 
                       Name = committee.Committee_Name, 
                       ...
                       ...
                     }).ToList());
//After Collecting information just update current value to base4string using following Syntax

activityList.ForEach(s=>s.id=(s.id==null?"noimage":Convert.ToBase4String(s.id));

DBContect does not recognizes some of in built functions such as Conversion Functions etc during execution.So execute linq query as it is with DBContext. Finally update list through loop and ForEach in list based loop which updates every pointed fields. Because It is not connect and related to DBContext every function will work here. :) .. I am using same and working fine :) — Minhajul Islam, Apr 11 '17 at 13:45

LINQ to Entities does not recognize the method 'System.String ToBase64String(Byte[])' method,

2 Answers2

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