asp.net mvc 防止開放重定向

/// <summary>
/// 防止開發重定向，篡改returnurl
/// </summary>
/// <param name="request"></param>
/// <param name="url"></param>
/// <returns></returns>
private static bool IsLocalUrl(string url)
{
      if (string.IsNullOrEmpty(url))
      {
            return false;
       }
       Uri absoluteUri;
       if (Uri.TryCreate(url, UriKind.Absolute, out absoluteUri))
       {
             return String.Equals(HttpContext.Current.Request.Url.Host, absoluteUri.Host, StringComparison.OrdinalIgnoreCase);
        }
         else
        {
                bool isLocal = !url.StartsWith("http:", StringComparison.OrdinalIgnoreCase) && !url.StartsWith("https:", StringComparison.OrdinalIgnoreCase) && Uri.IsWellFormedUriString(url, UriKind.Relative);
                return isLocal;
         }
 }