Fetchable.cs

using System;
using System.IO;
using System.Net;
using System.Text;
using System.Xml.Linq;

public abstract class Fetchable
{
    protected static String BuildURL(String baseURL, params Object[] pairs)
    {
        var sb = new StringBuilder();
        sb.Append(baseURL);
        if (pairs.Length > 0) {
            for (int i = 0; i < pairs.Length; i += 2) {
                sb.Append(i == 0 ? "?" : "&");
                sb.AppendFormat("{0}={1}", pairs[i], pairs[i + 1]);
            }
        }
        return sb.ToString();
    }

    public String URL { get; protected set; }
    public bool IsLoaded { get; private set; }

    public Fetchable()
    {
        URL = null;
        IsLoaded = false;
    }

    public Fetchable(String url)
    {
        URL = url;
        IsLoaded = false;
    }

    protected virtual bool OnPreFetch()
    {
        return true;
    }

    protected virtual void OnFetched(XDocument doc)
    {
        return;
    }

    public bool Fetch()
    {
        try {
            if (!OnPreFetch()) return true;
        } catch (Exception e) {
            Program.Server.Log(e);
            return false;
        }

        if (URL == null) {
            throw new InvalidOperationException("Cannot fetch; no URL given");
        }

        WebResponse response = null;

        var request = WebRequest.Create(URL);
        try {
            response = request.GetResponse();
            var stream = response.GetResponseStream();
            var text = new StreamReader(stream).ReadToEnd();
            var document = XDocument.Parse(text);

            OnFetched(document);

            return IsLoaded = true;
        } catch (Exception e) {
            Program.Server.Log(e);
            return false;
        } finally {
            if (response!= null) {
                response.Close();
            }
        }
    }
}