Could not load file or assembly 'System.Net.Http

Question

In my diagnostic view of my build output shows this conflict

There was a conflict between "System.Net.Http, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" and "System.Net.Http, Version=4.1.1.2, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a". (TaskId:20) "System.Net.Http, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" was chosen because it was primary and "System.Net.Http, Version=4.1.1.2, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" was not. (TaskId:20) References which depend on "System.Net.Http, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" [C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETFramework\v4.6.1\System.Net.Http.dll]. (TaskId:20)

I got here by adding the RestSharp nuget package. I was not having an issue until I installed this and I think one of the pieces that came with it may have caused this issue. I tried to uninstall it but that did not work.

Answer 1

Installing Nuget Package: System.Net.Http version 4.3.3 installs the correct Version=4.1.1.2

this will result in the following reference in your project file:

<Reference Include="System.Net.Http, Version=4.1.1.2, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">       <HintPath>..\..\..\..\packages\System.Net.Http.4.3.3\lib\net46\System.Net.Http.dll</HintPath> </Reference> 

Answer 2

If you using vs2017, some project will force u reference to system.net.http (4.2.0.0) When you install from nuget (version 4.3.3) and your system.net.http will be 4.1.1.2

-> it will be conflict

So in your web.config or app.config, you can change to 4.1.1.2 or 4.2.0.0 depend on which version was copy to bin folder when runtime

<dependentAssembly>         <assemblyIdentity name="System.Net.Http" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />         <bindingRedirect oldVersion="0.0.0.0-4.2.0.0" newVersion="4.1.1.2" />       </dependentAssembly>