System.* reference troubles when introducing NETStandard.Library dependency

35
votes

In a large solution with 52 projects (all net462), the latest version of some of our dependencies are now only built for NET standard. Therefore they depend on the NuGet package NETStandard.Library which in turn drags in a lot of other 4.3.x version of System.* packages which are normally in the .NET Framework itself.

As a result, some projects reference System.* libraries from the packages folder, while others reference System.* libraries from the .NET Framework.

This causes the well-known runtime issue, f.e.:

Message: System.IO.FileLoadException : Could not load file or assembly 'System.Net.Http, Version=4.1.1.2, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

Digging into the dependencies of the NETStandard.Library packages, we can see that the same issue also exists in these packages:

  • System.Collections.*
  • System.ComponentModel.*
  • System.Console
  • System.Globalization.*
  • System.IO.*
  • System.Linq.*
  • System.Net.*
  • System.ObjectModel
  • System.Reflection.*
  • System.Resources.ResourceManager
  • System.Runtime.*
  • System.Text.*
  • System.Threading.*
  • System.Xml.*

Normally this is fixed by installing the same package in the other projects, but we're dealing with a lot of projects and a lot of packages here and I don't want to blindly add all of those dependencies to all 52 projects.

This made me wonder whether anyone knows of an easy way to recover from this situation and to make all projects reference the correct package/DLL from the NuGet packages folder if they currently use the NET Framework internal one.

A simple VS-solution for net462 and net471 demonstrating the problem can be found here

1
c#nugetvisual-studio-2017
For .NET Framework other than 4.7.1 and above, you have no option at all, but to do what you are doing now. 4.7.1 and above ships the shim assemblies by default, and you don't need to do that any more. More in blogs.msdn.microsoft.com/dotnet/2017/10/17/… – Lex Li
4.7.1 still needs a few of these assemblies since there is a bug in 4.7.1 - it shipped with wrong assembly versions. – Martin Ullrich
@WouterHuysentruit, At this moment,it seems switch to latest framework 4.7.1 is a viable option. You can convert your comment to answer and accept it before you get a better solution, so it could help other community members who get the same issues. – Joy
Ah screw it. Updating Moq to 4.8.0 depends on System.Threading.Tasks.Extensions 4.4.0 and now a lot of unit tests are throwing the FileLoadException for System.Net.Http. I'm about to burn this place down :p – huysentruitw
Had something similar a few times, usually the matching .net version is incorrect and/or the build order, might not be the case, but worth checking anyway. – Netferret

1 Answers

12
votes

In the default project template System.Net.Http is added to the project as a reference, not as a nuget package.

In both of your solutions (4.6.1 and 4.7.1):

  • Project ClassLibrary has a dependency on System.Net.Http as a nuget package.

  • Project ConsoleApp1 has a dependency on System.Net.Http as a simple reference from .NET Framework

So, the issue is not related to Target Framework version.

To fix the issue add the same version of System.Net.Http as a nuget package to all projects (where it is used).

  1. Right-click the solution in Solution Explorer and choose Manage NuGet Packages for Solution...

  2. Switch to Installed tab

  3. Find System.Net.Http in the list, select it.

  4. Check current state:

Initial state of references to System.Net.Http nuget package

  1. Install the same version of the package (4.3.0 in your case) to ConsoleApp1 project.

  2. Check the result:

Fixed state of references to System.Net.Http nuget package

  1. Rebuild the solution.

Done.

Also, it's good practice to have package versions consolidated in your solution. Instead, you could have version conflicts during build time. Or, which is worse, runtime error like MethodNotFound because of binding redirect to another version of the dependency.

The reason for the problem with System.Net.Http is described here: Broken System.Net.Http 4.1.1-4.3.0 post-mortem in section How to prevent such situation in future? 2.1

As a result we identified 2 problematic OOB packages, which are not leaf-nodes in the platform itself, and have dependency from the platform on them - System.Net.Http and System.IO.Compression.

It means that the same System.Net.Http library is shipped within .NET Framework and as OOB (out-of-band) nuget package. And some nuget packages could reference nuget version of it. And here it comes the problem that I described at the very beginning.

So, you don't have to fix references to all System.* libraries. Only for these two: System.Net.Http and System.IO.Compression.