ASP.NET Web API项目中的System.Data.Common，System.Net.Http框架与Nuget程序集

Question

I am really confused about these two libraries that are included in the .NET Framework but are also available on Nuget. My instinct is to use the Nuget one as I would be getting more frequent updates etc. However Visual Studio even though I have referenced the one from nuget the msbuild uses one from .NET framework located at:

C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\MSBuild\Microsoft\Microsoft.NET.Build.Extensions\net461\lib

One workaround I found on github was to remove those libraries from the msbuild folder. But anytime I update VS Studio it brings them back there. Also the nuget package introduced some binding redirects. I can't count how many times the build goes fine and then Xth build gives an error that just makes no sense in regards to those assemblies.

Do you recommend removing the nuget packages and use the ones contained in the framework?

Answer 1

I got an answer from Jose Perez Rodriguez on Visual Studio Forum which explains it quite nicely:

Hello Jakub, and thanks for posting your question. Sorry it took us so long to respond. First of all, I do agree with you that this space in general is a bit confusing, but here is a TL;DR explanation of the issue. System.Net.Http and System.Data.Common packages to get updated more frequently, but only for the .NET Core implementation, not for .NET Framework which is what you are targetting. .NET Framework actually already has a version of these two assemblies installed in the GAC, but it is not the newest version (at least that is the case for frameworks < 4.7.2), and if your application has any dependency that is targeting .NET Standard 1.4+, then you will most likely need the very latest version of these assemblies in order for your app to work correctly at runtime. The latest version for .NET Framework is not the one in the GAC nor the one in the packages as I've said before, but instead the one found in the MSBuild Extensions folder that you found. Those versions are really the latest versions for .NET Framework, so when our build detects that you will need them, we inject them into your bin folder and we reference those in order to be able to not hit any runtime issues.

So all in all, the conclusion is that whichever workaround you found saying to delete those files from that directory is incorrect, and should never really be done as that may cause your app to have runtime issues. In order to let your app work properly, remove the binding redirects that were added automatically by NuGet when you installed the System.Net.Http and the Data.Common packages, and make sure you turn on AutoGenerateBindingRedirects. After taking those steps (and making sure that you restore that msbuild extensions folder since you said you deleted some files from it) your app in the end should have a copy of these assemblies in the bin folder with the latest version of them, and it should also have an app config with the right binding redirects generated at build time.

We will do a better job of explaining this behavior in github, since a lot of people are confused by this behavior. I hope this answers your question, but if not, please feel free to ask any follow up questions you may have.