您的代码看起来不错，我会尝试为 $webrequest 添加 HTTP_AUTHORIZATION 标头，如下所示:

Your code looks good, I would try adding HTTP_AUTHORIZATION header for $webrequest like this:

$webRequest.Headers.Add("AUTHORIZATION", "Basic YTph");

其中 YTph 是 username : password 的 base64 编码字符串.

Where YTph would be the base64encoded string for username : password.