title: Cannot Convert System.String to System.Uri
body: <p>I am using the Web Client Class to download files from the internet (Flickr actually).
  This works fine as long as I use : <code>WebClient().DownloadData(string)</code>  , however this locks up the UI as it is Not asynchronous.</p>
  
  <p>However when I try <code>WebClient().DownloadDatAsync(string)</code>, I get a compile error:
  "Unable to convert System.String to System.Uri".</p>
  
  <p>The string MediumUrl returns  <code>"http://farm4.static.flickr.com/2232/2232/someimage.jpg"</code></p>
  
  <p>So the question is how do I convert the string <code>"http://farm4.static.flickr.com/2232/2232/someimage.jpg"</code> to a Uri.</p>
  
  <p>Things I have tried-</p>
  
  <ol>
  <li>I have tried to cast it to Uri but that does not work either.   </li>
  <li><p>I have tried <code>Uri myuri = new uri(string)</code> - errors out as above. </p>
  
  <pre><code>foreach (Photo photo in allphotos)  
  {  
      //Console.WriteLine(String.Format("photo title is :{0}", photo.Title));
      objimage = new MemoryStream(wc.DownloadData(photo.MediumUrl));
      images.Add(new Pictures(new Bitmap(objimage), photo.MediumUrl, photo.Title));  
  }
  </code></pre></li>
  </ol>