C#静态磁场锁定

是否需要锁定\u userByNameQuery静态字段Yes/No和way?

public class SomeClass 
{
    static Func<Entities, string, IQueryable<User>> _userByNameQuery = 
        CompiledQuery.Compile<Entities, string, IQueryable<User>>
            ((context, userName) =>
                context.Users.Where(u => u.UserName.ToUpper() == userName));

    public bool UserNameExists(string userName)
    {
        userName = userName.ToUpper();
        return _userByNameQuery.Invoke(DataContext, userName).Count() > 0;
    }
}