aspnetcore/src/DataProtection/build/sources.props

<Project>
  <Import Project="$(DotNetRestoreSourcePropsPath)" Condition="'$(DotNetRestoreSourcePropsPath)' != ''"/>

  <PropertyGroup Label="RestoreSources">
    <RestoreSources>$(DotNetRestoreSources)</RestoreSources>
    <RestoreSources Condition="'$(DotNetBuildOffline)' != 'true' AND '$(AspNetUniverseBuildOffline)' != 'true' ">
      $(RestoreSources);
      https://dotnet.myget.org/F/dotnet-core/api/v3/index.json;
      https://dotnet.myget.org/F/aspnetcore-dev/api/v3/index.json;
      https://dotnet.myget.org/F/aspnetcore-tools/api/v3/index.json;
    </RestoreSources>
    <RestoreSources Condition="'$(DotNetBuildOffline)' != 'true'">
      $(RestoreSources);
      https://api.nuget.org/v3/index.json;
    </RestoreSources>
  </PropertyGroup>
</Project>