Minimal repro: unable to upgrade solution to 4.7.2

[wokwokwok1]

This relates to #481

Here is a minimal example that run successfully on .Net 4.6, and fails to run after upgrading to .Net 4.7.2
https://github.com/wokwokwok1/dotnet-46-project-upgrade-repro

You can view the various steps taken and the snapshot of the broken project as various phases through-out the upgrade attempt:

Re-targeting to 4.7.2

project snapshot:
https://github.com/wokwokwok1/dotnet-46-project-upgrade-repro/tree/net472_001_retarget

detail:
https://raw.githubusercontent.com/wokwokwok1/dotnet-46-project-upgrade-repro/net472_001_retarget/DemoApp/README.md

summary:

This does not work.

Compiler Error Message: CS0012: The type 'System.Object' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Runtime, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.

upgrading to package reference, as suggested in #481

project snapshot:
https://github.com/wokwokwok1/dotnet-46-project-upgrade-repro/tree/net472_002_migratePackages

detail:
https://raw.githubusercontent.com/wokwokwok1/dotnet-46-project-upgrade-repro/net472_002_migratePackages/DemoApp/README.md

summary:

This does not work.

Compiler Error Message: CS0012: The type 'System.Object' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Runtime, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.

attempting to manually pin dependency versions

project snapshot:
https://github.com/wokwokwok1/dotnet-46-project-upgrade-repro/tree/net472_003_manualDependencyResolution

detail:
https://raw.githubusercontent.com/wokwokwok1/dotnet-46-project-upgrade-repro/net472_003_manualDependencyResolution/DemoApp/README.md

summary:

This does not work, but a new error is seen.

Exception Details: System.IO.FileNotFoundException: Could not load file or assembly 'System.Runtime, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.

upgrading the project dependencies and applying 'magic' web.config fix

project snapshot:
https://github.com/wokwokwok1/dotnet-46-project-upgrade-repro/tree/net472_004_upgradeEverything

detail:
https://raw.githubusercontent.com/wokwokwok1/dotnet-46-project-upgrade-repro/net472_004_upgradeEverything/DemoApp/README.md

summary:

This resolved the issue and application now functions correctly.

The key to resolving this issue is from #542, where it was suggested to add assembly references directly to the web.config, like this:

 <system.web>
  <compilation debug="true" targetFramework="4.7.2">
    <assemblies>
      <add assembly="netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51"/>
    </assemblies>
  </compilation>
  <httpRuntime targetFramework="4.7.2"/>
  <httpModules/>
</system.web>

However, this was only a partial fix, and the complete fix required the addition of System.Runtime as well, like this:

<system.web>
  <compilation debug="true" targetFramework="4.7.2">
    <assemblies>
      <add assembly="netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51"/>
      <add assembly="System.Runtime, Version=4.0.20.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"/>
    </assemblies>
  </compilation>
  <httpRuntime targetFramework="4.7.2"/>
  <httpModules/>
</system.web>

This appears to full resolve the issue.

However, it is unclear why this is required, and is simply a random lucky guess that putting the dependency here will resolve the issue.

I leave this repro here, because I believe this is a bug.

[wokwokwok1]

Note: This repro has ~170 dependencies and is based off of a legacy .csproj template from a real project; however, it is extremely difficult to generate a reproducible failure condition from a 'fresh' branch new project. I've done the best I can here, hopefully it is enough to help identify some kind of root cause.

[GSPP]

I'm tracking related issues and information in a list. They are related to System.Net.Http, System.Runtime, System.IO, System.ValueTuple, System.Buffers and others.

https://github.com/dotnet/corefx/issues/32587
https://github.com/dotnet/corefx/issues/32561
#481
#567
#558
#887
#891
https://github.com/dotnet/corefx/issues/32610
https://github.com/dotnet/corefx/issues/30642
https://github.com/dotnet/corefx/issues/32757
#895
#877
#521
#295
#476
#184
#936
#941
https://github.com/dotnet/corefx/issues/33148
NuGet/Home#7440
https://github.com/dotnet/corefx/issues/31532
https://github.com/dotnet/corefx/issues/22781
https://github.com/dotnet/corefx/issues/23306
https://github.com/dotnet/corefx/issues/29622
https://github.com/dotnet/corefx/issues/9846
https://github.com/dotnet/corefx/issues/17522
https://github.com/dotnet/corefx/issues/25773

All of these have the same very few underlying issues.

.NET 4.7.2 helps with some but not all of these. You can look at my comments on some of these issues for some ideas on how to work around those problems. I also have a central list of ideas to try.

[GSPP]

it is extremely difficult to generate a reproducible failure condition

That might be because you have to delete the bin and obj folders:

Delete bin/obj folders (this often makes a difference because old assemblies are left there. VS clean does not remove them! This can make you believe that your solution works but it really just depends on old assemblies. I always have deleted these folders between tests to be sure.)

Fyi, my central list of workarounds has grown a bit with new ideas.

[wtgodbe]

We have many issues related to this problem in the repro, I'm consolidating them into #936