LINQ实体包含searchstring

Question

我已阅读Case insensitive Contains(string)，Why would Entity Framework not be able to use ToString() in a LINQ statement?以及其他许多问题，但我仍然无法找到正确的方法。

string searchString = "max";
private db = new DbContext();

IQueryable<Person> persons = from m in db.Persons
                          select m;
if (null != persons)
{
     //do what it should but marked as codesmell because of .ToStrong() with no culture
     persons = persons.Where(s =>
        s.person_name.ToLower().Contains(searchString.ToLower())); 

     //NotSupportedException
     persons = persons.Where(s =>
        cultureInfo.CompareInfo.IndexOf(s.person_name, searchString, CompareOptions.IgnoreCase) >= 0); 

     //NotSupportedException
     persons = persons.Where(s =>
        s.person_name.ToLower(CultureInfo.InvariantCulture).Contains(searchString.ToLower(CultureInfo.InvariantCulture)));  
}

在使用LINQ的数据库中进行不区分大小写的字符串搜索的正确方法是什么？