runtime: Simple .NET app throws `(407) Proxy Authentiation Required`

Related to https://github.com/PowerShell/PowerShell/issues/9495#issuecomment-627207665

Why

I was requested to create a .NET app as I’m having this issue.

The context of that request has to come from the fact that PowerShell uses .NET Core internally.

The issue summarized

In PowerShell v7.1 preview 2. On a company network, where direct access to the Internet is not allowed and a PAC file, distributed via DHCP, is used to to set the proxy that the computer should use. This gives issues in PowerShell. Namely this error:

```
VERBOSE: Repository details, Name = 'PSGallery', Location = 'https://www.powershellgallery.com   /api/v2'; IsTrusted = 'False'; IsRegistered = 'True'.
VERBOSE: Using the provider 'PowerShellGet' for searching packages.
VERBOSE: Using the specified source names : 'PSGallery'.
VERBOSE: Getting the provider object for the PackageManagement Provider 'NuGet'.
VERBOSE: The specified Location is 'https://www.powershellgallery.com/api/v2' and PackageManagementProvider is 'NuGet'.
WARNING: Unable to resolve package source 'https://www.powershellgallery.com/api/v2'.
VERBOSE: Total package yield:'0' for the specified package 'invokebuild'.
Install-Package: C:\program files\powershell\7-preview\Modules\PowerShellGet \PSModule.psm1:9709
Line |
9709 |  … talledPackages = PackageManagement\Install-Package @PSBoundParameters
| 
| No match was found for the specified search criteria and module name 'invokebuild'. Try
| Get-PSRepository to see all available registered module repositories.
```

When executing the Install-Module -name invokebuild -Verbose -Scope CurrentUser -Repository PSGallery -Force PowerShell cmdlet.

As described in the issue on the PowerShell repo that I link to in the beginning. I’ve tried setting the below in a PowerShell session (quickly listed).

• [System.AppContext]::SetSwitch("System.Net.Http.UseSocketsHttpHandler", $false)
• [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12]

• [system.net.webrequest]::defaultwebproxy = new-object   system.net.webproxy('http://10.90.100.24:8080')
  [system.net.webrequest]::defaultwebproxy.credentials =                                                                                    [System.Net.CredentialCache]::DefaultNetworkCredentials
  [system.net.webrequest]::defaultwebproxy.BypassProxyOnLocal = $true
  

Simple .NET app

using System;
namespace test
{
    class Program
    {
        static void Main(string[] args)
        {
            var a = System.Net.WebRequest.Create("https://ya.ru");
            var b = a.GetResponse();
            //Console.WriteLine("b");
        }
    }
}

Executing the above app (the project was created with dotnet new console, result in the following err:

Unhandled exception. System.Net.WebException: The remote server returned an error: (407) Proxy Authentication Required.
   at System.Net.HttpWebRequest.GetResponse()
   at test.Program.Main(String[] args) in C:\WORK\repos\test\Program.cs:line 10

From here

If any additional info is needed I’ll happily provide it. To the extent of my power and allowances. Also the PAC script in use might return more than one proxy addresses. But according to the issue (in the PowerShell repo) which I link to in the beginning, this should now be solved. So why could this error be occurring?

Thank you and looking forward to hear from you.