如何比较两个相同链接的列表？

Question

Im calling this class from a timer tick event each X seconds:

WebClient contents = new WebClient();
        List<string> links = new List<string>();
        public static List<string> FilteredLinks = new List<string>();
        List<string> Respones = new List<string>();
        public static List<List<string>> Threads = new List<List<string>>();

        public void Links(string FileName)
        {
            HtmlDocument doc = new HtmlDocument();
            doc.Load(FileName);
            foreach (HtmlNode link in doc.DocumentNode.SelectNodes("//a[@href]"))
            {
                HtmlAttribute att = link.Attributes["href"];
                if (att.Value.StartsWith("http://rotter.net/forum/scoops1"))
                {
                    links.Add(att.Value);
                }
            }

            for (int i = 0; i < links.Count; i++)
            {
                int f = links[i].IndexOf("#");
                string test = links[i].Substring(0, f);
                FilteredLinks.Add(test);
            }

links and FilteredLinks are both type List I need that it will check that if items already exist in the Lists don't add them again. Since its calling from a timer tick event so each X seconds the Lists are growing up with the same items over and over again.

Answer 1

Use HashSet instead of List. That way, you don't have to check for duplicate strings.

HashSet<string> links = new HashSet<string>();

A set is a collection that contains no duplicate elements,

http://msdn.microsoft.com/en-us/library/bb359438(v=vs.110).aspx

Answer 2

There are three ways to solve your problem

1. Use the right data structure. HashSet as LB pointed out .

2. Use Distinct to produce a list with only distinct after you done your adding

   links = link.Distinct();

3. Use Contains before you call add

if (!links.Contains(att.Value))  
   links.Add(att.Value);

If case is an issue you'll need to pass in one the StringComparer s eg

if (!links.Contains(att.Value, StringComparer.InvariantCultureIgnoreCase ))

Answer 3

You can make your own method for this

             public boolean isPresent(List mylist,String search)
             {
             for(String str: myList) {
             if(str.trim().contains(search))
             return true;
             }
             return false;
              }