Q:

Some part of your SQL statement is nested too deeply c# EF 5

I’m getting the following exception from EF 5:
Some part of your SQL statement is nested too deeply. Rewrite the query or break it up into smaller queries.
Here is my Query:
String username = “test”;
IEnumerable<Int32> roles;
IEnumerable<Int32> applications;

cnx.Users.Where ( it =>
( userName != null ?  it.name = = userName : true )  &&
( !roles.Any () || roles.Contains ( it.role_id ) ) &&
( ! applications.Any () || applications.Contains ( it.application_id ) ) )
               .Count ();

Users is a simple table. 
Roles and applications are both typeof IEnumerable and can be empty. 
How can I change my query, that it will work in EF 5 (.Net 4.0)?

A:

For me it looks like userName, roles and applications are parameters to the query, i.e. the data comes from your application and not from the database. In that case, I would write the query like this:
IQueryable<User> query = cnt.Users;
if(userName != null)
    query = query.Where(x => x.name == userName)
if(roles.Any())
    query = query.Where(x => roles.Contains(x.role_id));
if(applications.Any())
    query = query.Where(x => applications.Contains(x.application_id))

var result = query.Count();

This is a lot more readable and doesn't include unnecessary clutter into the resulting query.
Please note that roles and applications must not represent the unexecuted result of another query.
With "unexecuted result", I mean the following:
IEnumerable<Role> roles = context.Roles.Where(x => x = y);

