Unhandled Exception under Xamarin iOS

I'm using ssh.net in a Xamarin iOS application. When connecting to a sftp server with the iOS 's wifi turn off. I got this exception:
Unhandled Exception:
System.ObjectDisposedException: Safe handle has been closed occurred.
I debug the source code and found out that's because under Xamarin iOS
socket.ConnectAsync(args) return false when wifi is turned off.
SocketAbstraction.cs line 63 if (socket.ConnectAsync(args))
Then it run line 83 connectCompleted.Dispose();
At last function ConnectCompleted was called , where the exception occurred.

If I moved line 83 connectCompleted.Dispose() into below if statement like this:

       if (args.SocketError != SocketError.Success)
        {
            var socketError = (int) args.SocketError;

            // dispose Socket
            socket.Dispose();
            // dispose SocketAsyncEventArgs
            args.Dispose();

            // dispose ManualResetEvent
            connectCompleted.Dispose();

            throw new SocketException(socketError);
        }

then this bug is fixed.

socket.ConnectAsync(args) が処理される SocketAbstraction.cs の 63 行目付近と、connectCompleted が破棄される 83 行目を確認します。Wi-Fi を無効にした状態で Xamarin iOS SFTP 接続を再現し、ConnectCompleted を追跡します。失敗した接続が ObjectDisposedException を発生させず、期待されるソケットエラーを発生させれば完了です。