using System.Net;
using Microsoft.TeamFoundation;
using Microsoft.TeamFoundation.Client;
 
// Connect to a project collection by Uri
try
{
    Uri projectCollectionUri = new Uri("http://tfs2010:8080/tfs/MyCollection");
    TeamFoundationServer tfs = new TeamFoundationServer(projectCollectionUri, new UICredentialsProvider());
    tfs.EnsureAuthenticated();
}
catch (TeamFoundationServerUnauthorizedException ex)
{
    // handle access denied
}
catch (TeamFoundationServiceUnavailableException ex)
{
    // handle service unavailable
}
catch (WebException ex)
{
    // handle other web exception
}