title: Why is the member dictionary in this f# code always empty?
body: <p>I want to scrape a page for all the urls and put them in the dictionary. I created an class with an dictionary. But I can't seem to add elements into it.</p>
  
  <pre><code>type crawler =
  
       new()= {}
       member this.urls  = new Dictionary&lt;string,string&gt;()
       member this.start (url : string)=
          let hw = new HtmlWeb()
          let doc = hw.Load(url)
          let docNode = doc.DocumentNode
          let links = docNode.SelectNodes(".//a")
  
          for aLink in links do
              let href = aLink.GetAttributeValue("href"," ")
              if href.StartsWith("http://")  &amp;&amp; href.EndsWith(".html") then
                this.urls.Add(href, href)
  </code></pre>
  
  <p>Why is the dictionary urls empty?</p>