//①一般的List集合去重
List<string>list=new List<string>();
list.add("AAA");
list.add("AAA");
list.add("BBB");
list.add("AAA");

list=list.Distinct().ToList();

//②實體類List集合去重  
public class TravelTrafficInfo
    {
        /// <summary>
        /// 行程號
        /// </summary>
        public int JouneryNum { get; set; }
        /// <summary>
        /// 機票名稱
        /// </summary>
        public string TrafficName { get; set; }
    }
    public class TravelTrafficInfoComparer : IEqualityComparer<TravelTrafficInfo>
    {
    	 #region IEqualityComparer<User> 成員
        public bool Equals(TravelTrafficInfo x, TravelTrafficInfo y)
        {
        	 if (x.JouneryNum == y.JouneryNum && x.TrafficName == y.TrafficName)
        	 	  return true;
            else
                return false;
        }

        public int GetHashCode(TravelTrafficInfo obj)
        {
            return 0;
        }
        #endregion
    }
    //去除重複的航班
     List<TravelTrafficInfo> List = list.Distinct(new TravelTrafficInfoComparer()).ToList();
    
//③例如：Test是個實體類，有屬性Name、ID
List<Test>list=得到一個list集合;
list=list.Where(t=>t.Name("張三")).ToList();//得到名字中包含張三的