System.Net.Http.WinHttpResponseParser.GetResponseHeader C# (CSharp) Method

        public unsafe static bool GetResponseHeader(
            SafeWinHttpHandle requestHandle,
            uint infoLevel,
            ref char[] buffer,
            ref uint index,
            out string headerValue)
        {
            const int StackLimit = 128;

            Debug.Assert(buffer == null || (buffer != null && buffer.Length > StackLimit));

            int bufferLength;
            uint originalIndex = index;

            if (buffer == null)
            {
                bufferLength = StackLimit;
                char* pBuffer = stackalloc char[bufferLength];
                if (QueryHeaders(requestHandle, infoLevel, pBuffer, ref bufferLength, ref index))
                {
                    headerValue = new string(pBuffer, 0, bufferLength);
                    return true;
                }
            }
            else
            {
                bufferLength = buffer.Length;
                fixed (char* pBuffer = buffer)
                {
                    if (QueryHeaders(requestHandle, infoLevel, pBuffer, ref bufferLength, ref index))
                    {
                        headerValue = new string(pBuffer, 0, bufferLength);
                        return true;
                    }
                }
            }

            int lastError = Marshal.GetLastWin32Error();

            if (lastError == Interop.WinHttp.ERROR_WINHTTP_HEADER_NOT_FOUND)
            {
                headerValue = null;
                return false;
            }

            if (lastError == Interop.WinHttp.ERROR_INSUFFICIENT_BUFFER)
            {
                // WinHttpQueryHeaders may advance the index even when it fails due to insufficient buffer,
                // so we set the index back to its original value so we can retry retrieving the same
                // index again with a larger buffer.
                index = originalIndex;

                buffer = new char[bufferLength];
                return GetResponseHeader(requestHandle, infoLevel, ref buffer, ref index, out headerValue);
            }

            throw WinHttpException.CreateExceptionUsingError(lastError);
        }

        public static void AddResponseCookiesToContainer(WinHttpRequestState state)
        {
            HttpRequestMessage request         = state.RequestMessage;
            SafeWinHttpHandle  requestHandle   = state.RequestHandle;
            CookieContainer    cookieContainer = state.Handler.CookieContainer;

            Debug.Assert(state.Handler.CookieUsePolicy == CookieUsePolicy.UseSpecifiedCookieContainer);
            Debug.Assert(cookieContainer != null);

            // Get 'Set-Cookie' headers from response.
            char[] buffer = null;
            uint   index  = 0;
            string cookieHeader;

            while (WinHttpResponseParser.GetResponseHeader(
                       requestHandle, Interop.WinHttp.WINHTTP_QUERY_SET_COOKIE, ref buffer, ref index, out cookieHeader))
            {
                try
                {
                    cookieContainer.SetCookies(request.RequestUri, cookieHeader);
                    if (NetEventSource.Log.IsEnabled())
                    {
                        NetEventSource.Info(cookieContainer, $"Added cookie: {cookieHeader}");
                    }
                }
                catch (CookieException)
                {
                    // We ignore malformed cookies in the response.
                    if (NetEventSource.Log.IsEnabled())
                    {
                        NetEventSource.Error(cookieContainer, $"Ignoring invalid cookie: {cookieHeader}");
                    }
                }
            }
        }