public virtual void RemoveCredential(NSURLCredential credential, NSURLProtectionSpace forProtectionSpace, Dictionary <NSObject, AnyObject> options)
 {
 }
 public virtual void SetCredential(NSURLCredential credential, NSURLProtectionSpace forProtectionSpace)
 {
 }
 public NSURLAuthenticationChallenge(NSURLProtectionSpace protectionSpace, [Optional] NSURLCredential proposedCredential, int previousFailureCount, [Optional] NSURLResponse failureResponse, [Optional] NSError error, NSURLAuthenticationChallengeSender sender)
 {
 }