List集合的動態查詢Func語法

　　List集合遇到動態查詢情況，通常寫着很麻煩，這個時候Func就派上用場了。給Func賦值他就參與查詢，不賦值就不會參與查詢。

public static void Select3()
{
    List<UserInfo> listUserInfo = new List<UserInfo>() { new UserInfo { ID = 1, Name = "A", Age = 20 }, new UserInfo { ID = 2, Name = "B", Age = 20 }, new UserInfo { ID = 3, Name = "C", Age = 20 } };  //實例化集合
    Func<UserInfo, bool> filterID = x => true, filterName = x => true;
    filterID = x => x.Age == 20;
    filterName = x => x.Name != "C";
    List<UserInfo> listWhere = listUserInfo.Where(filterID).Where(filterName).ToList();
    listWhere.ForEach(p => Console.WriteLine("ID:" + p.ID + " Name:" + p.Name + " Age:" + p.Age));
    Console.ReadKey();
}