System.Net.WebSockets.ManagedWebSocket.SendCloseFrameAsync C# (CSharp) Method

        private async Task SendCloseFrameAsync(WebSocketCloseStatus closeStatus, string closeStatusDescription, CancellationToken cancellationToken)
        {
            // Close payload is two bytes containing the close status followed by a UTF8-encoding of the status description, if it exists.

            byte[] buffer;
            if (string.IsNullOrEmpty(closeStatusDescription))
            {
                buffer = new byte[2];
            }
            else
            {
                buffer = new byte[2 + s_textEncoding.GetByteCount(closeStatusDescription)];
                int encodedLength = s_textEncoding.GetBytes(closeStatusDescription, 0, closeStatusDescription.Length, buffer, 2);
                Debug.Assert(buffer.Length - 2 == encodedLength, $"GetByteCount and GetBytes encoded count didn't match");
            }

            ushort closeStatusValue = (ushort)closeStatus;
            buffer[0] = (byte)(closeStatusValue >> 8);
            buffer[1] = (byte)(closeStatusValue & 0xFF);

            await SendFrameAsync(MessageOpcode.Close, true, new ArraySegment<byte>(buffer), cancellationToken).ConfigureAwait(false);

            lock (StateUpdateLock)
            {
                _sentCloseFrame = true;
                if (_state <= WebSocketState.CloseReceived)
                {
                    _state = WebSocketState.CloseSent;
                }
            }
        }