System.* reference troubles when introducing NETStandard.Library dependency

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:

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

6. Check the result:

7. 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.