void Main()
{
    var Persons = new List<Person>(){
        new Person{
            Name="Алексей",
            Surname="Фоминых"
        },
        new Person{
            Name="Алексей",
            Surname="Дуров"
        },
    };
    var t = Persons.AsQueryable();

    var f = "Фоминых Алексей";

    foreach (var it in f.ToLower().Split(' '))
    {
        t = t.Where(x=>(x.Name+x.Surname).ToLower().Contains(it));
    }
    Debug.Assert(t.Count()==1);
}

class Person
{
    public string Name {get;set;}
    public string Surname {get;set;}
}