Same code in Sandbox solution generates error

Question

I am using following code in a Web Part to read Rss (atom). Same Web Part works in Farm Solution but generates error (don't know what) in a Sandbox solution.

 WebClient wc = new WebClient();
 wc.Credentials = new NetworkCredential("myuserName", "myPassword");

IEnumerable<myClass> feeds = null;
using (System.IO.Stream stream = wc.OpenRead(myfeed))
        {
            XDocument d = XDocument.Load(stream);
            XNamespace ns = XNamespace.Get("http://www.w3.org/2005/Atom");

            feeds = d.Root.Descendants(ns + "entry").Select(e =>
                new myClass
                {
                    Title = e.Element(ns + "title").Value,
                    Description = e.Element(ns + "summary").Value,
                    Link = e.Element(ns + "link").Value
                });
        }

 foreach (Rss item in feeds)
 {
     //render items
 }

Answer 1

Most likely, it happens bacause it is impossible to "Create a Web Part that interacts with a Web service or a Windows Communication Foundation (WCF) service." in sandboxed solutions.

As a workaround you can create full-trust proxy.

Some links which could be usefull:

• Walkthrough: Creating and Calling a Full-Trust Proxy Operation
• SharePoint 2010 Sandboxed soulutions: Full Trust Proxies