List多个字段标识过滤

class Program
{
 　　public static void Main(string[] args)
　　{

　　　　List<T> list = new List<T>();
　　　　list.Add(new T() { orderid = 1, houseid = 1 });
　　　　list.Add(new T() { orderid = 1, houseid = 1 });
　　　　list.Add(new T() { orderid = 1, houseid = 2 });
　　　　list.Add(new T() { orderid = 1, houseid =3 });
　　　　list.Add(new T() { orderid = 2, houseid = 1 });
　　　　list.Add(new T() { orderid = 2, houseid = 2 });
　　　　list.Add(new T() { orderid = 2, houseid = 2 });
　　　　list.Add(new T() { orderid = 2, houseid = 3 });

　　　　var _list= list.Where((x, y) => list.FindIndex(a => a.orderid == x.orderid&&a.houseid==x.houseid) == y);

　　}
　　public class T {
　　　　public long orderid { get; set; }
　　　　public long houseid { get; set; }
　　}
}

_list 结果如下：

new T() { orderid = 1, houseid = 1 }
new T() { orderid = 1, houseid = 2 }
new T() { orderid = 1, houseid = 3 }
new T() { orderid = 2, houseid = 1 }
new T() { orderid = 2, houseid = 2 }
new T() { orderid = 2, houseid = 3 }