node.Attributes["class"].Value

String val;
if(node.Attributes["class"] != null)
{
  val = node.Attributes["class"].Value;
}

public static class HtmlAgilityExtender
{
    public static String ValueOrDefault(this HtmlAttribute attr)
    {
        return (attr != null) ? attr.Value : String.Empty;
    }
}

node.Attributes["class"].ValueOrDefault();

String abc = String.Empty;
      if (tag.Attributes.Contains(@"type"))
      {
          abc = tag.Attributes[@"type"].Value;
      }

String getURL(){
return @"some site address";
}
List<string> Internalscripts()
    {
        HtmlAgilityPack.HtmlDocument doc = new HtmlWeb().Load((@"" + getURL()));
        //Getting All the JavaScript in List
        HtmlNodeCollection javascripts = doc.DocumentNode.SelectNodes("//script");
        List<string> scriptTags = new List<string>();
        foreach (HtmlNode script in javascripts)
        {
            if(!script.Attributes.Contains(@"src"))
            {
                scriptTags.Add(script.InnerHtml);
            }
        }
        return scriptTags;
    }