Specified method is not supported MySql Entity Framwork 6 - mysql

Question

I am trying to run the following Linq query from MySQL client
query = query.Where(c => c.CustomerRoles
.Select(cr => cr.Id)
.Intersect(customerRoleIds)
.Any()
);
This code looks okay, but gives the error:
System.NotSupportedException: Specified method is not supported.at MySql.Data.Entity.SqlGenerator.Visit(DbIntersectExpression expression)
This looks to me like an issue with .Intersect. Can anybody tell me the cause of this error and how to fix it?

Answer 1

i think #GertArnold's post is a correct and best of the answers, but i'm wonder why have you gotten NotSupportedException yet ? so the problem should not be from intersect probably.
where is customerRoleIds come from ? is it IQueryable<T> ?
break the query, and complete it step by step.
if you don't get exception at this lines:
var a = query.Select(c => new {
c,
CustomerRoleIDList = c.CustomerRoles.Select(cr => cr.Id).AsEnumerable()
})
.ToList();
var b = customerRoleIds.ToList();
you must get the result by this:
var b = query.Where(c => c.CustomerRoles.any(u => customerRoleIds.Contains(u.Id)))
.ToList();
if you get exception by above query, you can try this final solution to fetch data first, but note by this, all data will be fetched in memory first:
var a = query.Select(c => new {
c,
CustomerRoleIDList = c.CustomerRoles.Select(cr => cr.Id).AsEnumerable()
})
.ToList();
var b = a.Where(c => c.CustomerRoleIDList.any(u => customerRoleIds.Contains(u)))
.Select(u => u.c)
.ToList();

Answer 2

Using Intersect or Except is probably always troublesome with LINQ to a SQL backend. With Sql Server they may produce horrible SQL queries.
Usually there is support for Contains because that easily translates to a SQL IN statement. Your query can be rewritten as
query = query.Where(c => c.CustomerRoles
.Any(cr => customerRoleIds.Contains(cr.Id)));
I don't think that customerRoleIds will contain many items (typically there won't be hundreds of roles), otherwise you should take care not to hit the maximum number of items allowed in an IN statement.

Answer 3

query.Where(c => c.CustomerRoles
.Any(v=>customerRoleIds.Any(e=>e == v.Id))
.Select(cr => cr.Id))
.ToList();

Answer 4

Try adding toList() before intersect, that should enumerate results locally instead running on MySql, you will get performance hit thought.
query = query.Where(c => c.CustomerRoles.Select(cr => cr.Id)).ToList().Intersect(customerRoleIds);