Fixing Google BigQuery Auth Proxying

The article explains that when using Google BigQuery client libraries in C# applications behind a proxy, authentication and token refresh requests fail because they ignore proxy settings, even when data queries are correctly proxied. The solution is to set a proxied `GoogleCredential` (created using `CreateWithHttpClientFactory`) on the `GoogleCredential` property of `BigQueryClientBuilder`, rather than the `Credential` property, to ensure OAuth token requests also route through the proxy.

builder.Credential = credential; - Fails to route authentication traffic through the proxy.builder.GoogleCredential = credential; - Successfully routes OAuth token requests through the proxy.If your C application runs behind a proxy, you have probably run into an annoying issue with the Google BigQuery client libraries: your BigQuery query calls route through the proxy perfectly by setting the HttpClientFactory property on the BigQueryClientBuilder , but the authentication and token refresh requests ignore the proxy entirely and attempt to hit the standard network, causing timeouts. To resolve this, set a proxied GoogleCredential to the GoogleCredential property instead of the Credential property on the client builder. Example code: using System.Net; using Google.Apis.Auth.OAuth2; using Google.Apis.Http; using Google.Cloud.BigQuery.V2; // 1. Configure your proxy IWebProxy proxySettings = new WebProxy "http://your-proxy-host:8080", bypassOnLocal: true { Credentials = new NetworkCredential "username", "password" }; // 2. Wrap it inside Google's API HttpClientFactory HttpClientFactory proxyClientFactory = HttpClientFactory.ForProxy proxySettings ; // 3. Load credentials and create a new credential using the proxied http client factory GoogleCredential credential = await GoogleCredential.FromFileAsync "path/to/service-account.json" ; credential = credential.CreateWithHttpClientFactory proxyClientFactory ; // 4. Construct the client BigQueryClient bigQueryClient = new BigQueryClientBuilder { ProjectId = "your-google-cloud-project-id", HttpClientFactory = proxyClientFactory, // Proxies BigQuery data calls GoogleCredential = credential // CRITICAL: Proxies Auth/token calls }.Build ;