具有基本身份验证的HttpWebRequest失败，DefaultNetworkCredentials出现401错误

我正在使用本地Web服务器(IIS，Windows 8)测试应用程序，该站点需要基本身份验证，并且只要我明确地传递我的凭据，一切都可以正常进行:

I am testing an application with a local Web server (IIS, Windows 8), the site requires Basic authentication, and as long as I explicitly pass my credentials, everything works fine:

request.Credentials = new NetworkCredential("User", "Password", "Domain");
request.PreAuthenticate = true;

但是我想使用集成安全性，因此我尝试如下更改第一行:

But I would like to use integrated security, so I tried to change the first line as follows:

request.Credentials = CredentialCache.DefaultNetworkCredentials;

(我也尝试了DefaultCredentials)

(I also tried DefaultCredentials)

我检查了Fiddler的网络流量，发现在第二种情况下Http请求是在没有授权标头的情况下发送的，因此失败就不足为奇了.但是为什么呢?

I checked the network traffic with Fiddler, and I see that in the second case Http request is sent without an authorization header, so it's not surprising that it fails. But why?

更新.我相信我误解了默认凭据概念. DefaultNetworkCredentials可能不用于生成基本身份验证标头，它必须是用户/密码对.因此，这种行为是设计使然.

UPDATE. I believe I misunderstood default credentials concept. DefaultNetworkCredentials may not be used to generate basic authentication header, it must be a user/password pair. So this behavior is by design.