NuGet restore blocked by network isolation in VerifyImagesWithWebApps Test

[lbussell]

Pipeline: dotnet-framework-docker-official #2900408

The Test stage fails across all 4 OS variants with the same root cause: nuget restore inside the test container cannot reach api.nuget.org due to 1ES Pipeline Template network isolation.

Failed Jobs

Job	OS	Test
Windows1809_amd64	ltsc2019	VerifyImagesWithWebApps (4.8)
Windows2022_amd64	ltsc2022	VerifyImagesWithWebApps (4.8.1)
Windows2025_amd64	ltsc2025	VerifyImagesWithWebApps (4.8.1)
WindowsLtsc2016_amd64	ltsc2016	VerifyImagesWithWebApps (4.8)

Root Cause

The webapp-4.8 test project Dockerfile runs nuget restore at build time, but the Docker build context (tests/.../projects/webapp-4.8/) does not include a NuGet.config. The container falls back to the default NuGet configuration pointing to https://api.nuget.org/v3/index.json.

The repo root NuGet.config uses the Azure DevOps public feed (pkgs.dev.azure.com/dnceng/public/...), which would work under network isolation, but it is not available inside the test container's Docker build context.

Packages Affected

From tests/.../projects/webapp-4.8/packages.config:

• Microsoft.Net.Compilers 2.6.1
• Microsoft.CodeDom.Providers.DotNetCompilerPlatform 1.0.8

Suggested Fix

Copy or generate a NuGet.config into the webapp test project build context that uses the internal Azure DevOps feed (https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-public/nuget/v3/index.json) instead of relying on the default api.nuget.org source.