public static IEnumerable<TSource> DistinctBy<TSource, TKey> (this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
{
? ? HashSet<TKey> seenKeys = new HashSet<TKey>();
? ? foreach (TSource element in source)
? ? {
? ? ? ? if (seenKeys.Add(keySelector(element)))
? ? ? ? {
? ? ? ? ? ? yield return element;
? ? ? ? }
? ? }
}

var query = people.DistinctBy(p => new { p.Id, p.Name });

var query = people.DistinctBy(p => p.Id);

  //
        // 摘要:
        //     通過使用默認的相等比較器對值進行比較，生成兩個序列的差集。
        //
        // 參數:
        //   first:
        //     System.Collections.Generic.IEnumerable`1 也不是在其元素 second 將返回。
        //
        //   second:
        //     System.Collections.Generic.IEnumerable`1 同時出現在第一個序列的元素將導致從返回的序列中移除這些元素。
        //
        // 類型參數:
        //   TSource:
        //     輸入序列中的元素的類型。
        //
        // 返回結果:
        //     包含這兩個序列的元素的差集的序列。
        //
        // 異常:
        //   T:System.ArgumentNullException:
        //     first 或 second 為 null。
        public static IEnumerable<TSource> Except<TSource>(this IEnumerable<TSource> first, IEnumerable<TSource> second);

public class ChannelTvListInfo
    {
        public string TVName { get; set; } //節目列表名字
        public string LastWriteTime { get; set; }//最后編輯文件時間
    }

private List<ChannelTvListInfo> lstNewTvInfo, lstOldTvInfo = new List<ChannelTvListInfo>();
		private void button3_Click(object sender, EventArgs e)
		{       //通過下載后與定時下載的目錄文件進行名字及最后編輯文件的時間進行對比更新
			lstNewTvInfo = listFTPFiles("60.208.140.xxx", "", "");
			DirectoryInfo TheFolder = new DirectoryInfo(@"D:\ChannelTvXML\");
			foreach (FileInfo NextFile in TheFolder.GetFileSystemInfos())
			{
				lstOldTvInfo.Add(new ChannelTvListInfo { TVName = NextFile.Name, LastWriteTime = 
NextFile.LastWriteTime.ToString("yyyy/MM/dd hh:mm tt") });
			}
			
		}
		public List<ChannelTvListInfo> listFTPFiles(string FTPAddress, string username, string password)
		{
			List<ChannelTvListInfo> listinfo = new List<ChannelTvListInfo>();
			using (FtpConnection ftp = new FtpConnection(FTPAddress, username, password))
			{
				ftp.Open();
				ftp.Login();
				foreach (var file in ftp.GetFiles("/"))
				{
					listinfo.Add(new ChannelTvListInfo
					{
						TVName = file.Name,
						LastWriteTime = Convert.ToDateTime(file.LastWriteTime).ToString("yyyy/MM/dd hh:mm tt")
					});
				}
				ftp.Dispose();
				ftp.Close();
			}
			return listinfo;
		}

var result = lstNewTvInfo.Except(lstOldTvInfo.Where(x=>x.TVName.Contains("四川")), new ProductComparer()).ToList();

	public class ProductComparer : IEqualityComparer<ChannelTvListInfo>
	{
		// Products are equal if their names and product numbers are equal.
		public bool Equals(ChannelTvListInfo x, ChannelTvListInfo y)
		{
 
			//Check whether the compared objects reference the same data.
			if (Object.ReferenceEquals(x, y)) return true;
 
			//Check whether any of the compared objects is null.
			if (Object.ReferenceEquals(x, null) || Object.ReferenceEquals(y, null))
				return false;
 
			//Check whether the products' properties are equal.
			return x.TVName == y.TVName && x.LastWriteTime == y.LastWriteTime;
		}
 
		// If Equals() returns true for a pair of objects 
		// then GetHashCode() must return the same value for these objects.
 
		public int GetHashCode(ChannelTvListInfo product)
		{
			//Check whether the object is null
			if (Object.ReferenceEquals(product, null)) return 0;
 
			//Get hash code for the Name field if it is not null.
			int hashProductName = product.TVName == null ? 0 : product.TVName.GetHashCode();
 
			//Get hash code for the Code field.
			int hashProductCode = product.LastWriteTime.GetHashCode();
 
			//Calculate the hash code for the product.
			return hashProductName ^ hashProductCode;
		}
 
	}