System.Net.Http.HttpClient.PrepareRequestMessage C# (CSharp) Method

        private void PrepareRequestMessage(HttpRequestMessage request)
        {
            Uri requestUri = null;
            if ((request.RequestUri == null) && (_baseAddress == null))
            {
                throw new InvalidOperationException(SR.net_http_client_invalid_requesturi);
            }
            if (request.RequestUri == null)
            {
                requestUri = _baseAddress;
            }
            else
            {
                // If the request Uri is an absolute Uri, just use it. Otherwise try to combine it with the base Uri.
                if (!request.RequestUri.IsAbsoluteUri)
                {
                    if (_baseAddress == null)
                    {
                        throw new InvalidOperationException(SR.net_http_client_invalid_requesturi);
                    }
                    else
                    {
                        requestUri = new Uri(_baseAddress, request.RequestUri);
                    }
                }
            }

            // We modified the original request Uri. Assign the new Uri to the request message.
            if (requestUri != null)
            {
                request.RequestUri = requestUri;
            }

            // Add default headers
            if (_defaultRequestHeaders != null)
            {
                request.Headers.AddHeaders(_defaultRequestHeaders);
            }
        }