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(rèn)的相等比較器對值進(jìn)行比較，生成兩個序列的差集。
        //
        // 參數(shù):
        //   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(xiàn)在第一個序列的元素將導(dǎo)致從返回的序列中移除這些元素。
        //
        // 類型參數(shù):
        //   TSource:
        //     輸入序列中的元素的類型。
        //
        // 返回結(jié)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(jié)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(jìn)行名字及最后編輯文件的時間進(jìn)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;
		}
 
	}