Adapted from the DotNetOpenAuth > Samples > OpenIdProviderMVC example

OpenIdPartialController.cs

internal static OpenIdProvider OpenIdProvider = new OpenIdProvider();

public ActionResult Id()
{
    if (Request.AcceptTypes != null && Request.AcceptTypes.Contains("application/xrds+xml"))
    {
        ViewData["OPIdentifier"] = true;
    }
    return View();
}