使用哈希码检测List <string>的元素是否已更改C#的示例

Question

我有一个List,它根据一些XML元素的Linq查询每分钟更新一次.

xml会不时发生变化.有人建议我可以使用Hashcode来确定列表中的任何字符串是否已更改.

我已经看到了一些Md5哈希码计算的例子只是一个字符串,但不是列表...有人能告诉我一个用列表做这个的方法吗？

我试过像int test = list1.GetHashCode这样简单的东西; 但无论列表中的内容如何,​​代码都是相同的......

这是带有链接查询的整个方法,最后是所有..note SequenceEqual:

        private void GetTrackInfo()
    {
        _currentTitles1.Clear();
        var savedxmltracks = new XDocument();

        listBox1.Items.Clear();
        WebClient webClient = new WebClient();

        XmlDocument xmltracks = new XmlDataDocument();
        try
        {
            xmltracks.Load(_NPUrl);
            xmltracks.Save("xmltracks.xml");
        }
        catch (WebException ex)
        {
            StatusLabel1.Text = ex.Message;
        }

        try
        {
             savedxmltracks = XDocument.Load("xmltracks.xml");
        }
        catch (Exception ex)
        {
            StatusLabel1.Text = ex.Message;
        }


        var dateQuery = from c in savedxmltracks.Descendants("content")
                           select c;

        _count = savedxmltracks.Element("content").Element("collection").Attribute("count").Value;

        var tracksQuery1 = from c in savedxmltracks.Descendants("data")
                           select new
                           {
                               title = c.Attribute("title").Value,
                               imageurl = c.Attribute("image").Value,
                               price = c.Attribute("price").Value,
                               description = c.Attribute("productdescription").Value,
                               qualifier = c.Attribute("pricequalifier").Value

                           };

        var xml = new XDocument(new XDeclaration("1.0", "utf-8", "yes"),
        new XElement("LastUsedSettings",
            new XElement("TimerInterval",
                new XElement("Interval", Convert.ToString(numericUpDown1.Value))),
            new XElement("NowPlayingURL",
                new XElement("URL", _NPUrl)),
            new XElement("Email", emailAddress),
            new XElement("LastUpdated", DateTime.Now.ToString())));
        XElement StoreItems = new XElement("StoreItems");


        int i = 0;
        foreach (var c in tracksQuery1)
        {

            if (c.title.Length <= 40 & c.qualifier.Length <= 12 & i < 10)
            {

                if (c.title != null) _title1 = c.title;
                if (c.imageurl != null) _imageUrl = c.imageurl;
                if (c.price != null) _price = c.price;
                if (c.description != null) _productDescription = c.description;
                if (c.qualifier != null) _priceQualifier = c.qualifier;
                //}
                StoreItems.Add(new XElement("Title" + i.ToString(), _title1));
                _currentTitles1.Add(_title1);
                if (_oldTitles1.Count > 0)
                {
                    Console.WriteLine("OldTitle: {0}, NewTitle: {1}", _oldTitles1[i], _currentTitles1[i]);
                }
                StoreItems.Add(new XElement("Price" + i.ToString(), _price));
                StoreItems.Add(new XElement("Description" + i.ToString(), _productDescription));
                StoreItems.Add(new XElement("PriceQualifier" + i.ToString(), _priceQualifier));

                listBox1.Items.Add("Title: " + _title1);
                listBox1.Items.Add("Image URL: " + _imageUrl);
                listBox1.Items.Add("Price: " + _price);
                listBox1.Items.Add("Description: " + _productDescription);
                listBox1.Items.Add("PriceQualifier: " + _priceQualifier);

                try
                {
                    imageData = webClient.DownloadData(_imageUrl);
                }
                catch (WebException ex)
                {
                    StatusLabel1.Text = ex.Message;
                }

                MemoryStream stream = new MemoryStream(imageData);
                Image img = Image.FromStream(stream);
                //Image saveimage = img;
                //saveimage.Save("pic.jpg");

                img.Save("pic" + i.ToString() + ".jpg");

                stream.Close();



                i++;
            }
        }



        //Console.WriteLine("Count: " + _count);
        Console.WriteLine("oldTitles Count: " + _oldTitles1.Count.ToString());
        Console.WriteLine("currentTitles Count: " + _currentTitles1.Count.ToString());

        if (_oldTitles1.Count == 0) _oldTitles1 = _currentTitles1;

        if (!_oldTitles1.SequenceEqual(_currentTitles1))
        {
            Console.WriteLine("Items Changed!");
            SendMail();
            _oldTitles1 = _currentTitles1;
        }


        xml.Root.Add(StoreItems);
        xml.Save("settings.xml");


    }

Answer 1

为什么不只是使用ObservableCollection并监视对列表的更改？

如果你真的想要散列整个列表,你可能会这样做:

List<String> words;
int hash = String.Join("", words.ToArray()).GetHashCode();

我认为MD5可能过度,你不需要加密安全散列函数来完成这项任务.

参考:String.Join和String.GetHashCode