How do you add dynamic 'where' clauses to a linq query?

Question

I\'ve got a User table with a bitmask that contains the user\'s roles. The linq query below returns all the users whose roles include 1, 4 or 16.

var users          


        

Answer 1

Here's one way of adding a variable number of where clauses to your LINQ query. Note that I haven't touched your bitmask logic, I just focused on the multiple wheres.

// C#
private List GetUsersFromRoles(uint[] UserRoles)
{
   var users = dc.Users;

   foreach (uint role in UserRoles)
   {
      users = users.Where(u => (u.UserRolesBitmask & role) == role);
   }

   return users.ToList();
}

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EDIT: Actually, this will AND the where clauses and you wanted to OR them. The following approach (a inner join) works in LINQ to Objects but can not be translated to SQL with LINQ to SQL:

var result = from user in Users
             from role in UserRoles
             where (user.UserRolesBitmask & role) == role
             select user;