Linq利用Distinct去除重复项问题(可自己指定)

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:
        //     通过使用默认的相等比较器对值进行比较，生成两个序列的差集。
        //
        // 参数:
        //   first:
        //     System.Collections.Generic.IEnumerable`1 也不是在其元素 second 将返回。
        //
        //   second:
        //     System.Collections.Generic.IEnumerable`1 同时出现在第一个序列的元素将导致从返回的序列中移除这些元素。
        //
        // 类型参数:
        //   TSource:
        //     输入序列中的元素的类型。
        //
        // 返回结果:
        //     包含这两个序列的元素的差集的序列。
        //
        // 异常:
        //   T:System.ArgumentNullException:
        //     first 或 second 为 null。
        public static IEnumerable<TSource> Except<TSource>(this IEnumerable<TSource> first, IEnumerable<TSource> second);

public class ChannelTvListInfo
    {
        public string TVName { get; set; } //节目列表名字
        public string LastWriteTime { get; set; }//最后编辑文件时间
    }

private List<ChannelTvListInfo> lstNewTvInfo, lstOldTvInfo = new List<ChannelTvListInfo>();
		private void button3_Click(object sender, EventArgs e)
		{       //通过下载后与定时下载的目录文件进行名字及最后编辑文件的时间进行对比更新
			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;
		}
 
	}