.net - Strange issue with System.Net.Http 4.2.0.0 not found

Question

I have a strange issue, which drives me crazy…

I have a simple Class Library Project (Full .NET Framework, 4.6.1) with a wrapper class for functionality around Cosmos DB. Therefore I have added the “Microsoft.Azure.DocumentDB” NuGet Package 1.19.1 to this project. Other than that, I have a reference to the “Newtonsoft.Json” NuGet Package 10.0.3, as well as to a couple of "Microsoft.Diagnostics.EventFlow.*" NuGet Packages.

So far, everything compiles without any error.

But as soon as I hit my wrapper class – consumed from a simple Service Fabric Stateless Service (Full .NET Framework 4.6.1) – and try to execute the following line of code:

_docClient = new DocumentClient(new Uri(cosmosDbEndpointUrl), cosmosDbAuthKey);

I get this strange error at runtime:

System.IO.FileNotFoundException occurred HResult=0x80070002
Message=Could not load file or assembly 'System.Net.Http, Version=4.2.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.
Source= StackTrace: at Microsoft.Azure.Documents.Client.DocumentClient.Initialize(Uri serviceEndpoint, ConnectionPolicy connectionPolicy, Nullable1 desiredConsistencyLevel) at Microsoft.Azure.Documents.Client.DocumentClient..ctor(Uri serviceEndpoint, String authKeyOrResourceToken, ConnectionPolicy connectionPolicy, Nullable1 desiredConsistencyLevel)

Inner Exception 1: FileNotFoundException: Could not load file or assembly 'System.Net.Http, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.

I have absolutely no clue, why the System.Net.Http assembly is not found at all – there is even a assembly reference in my class library project to the .Net Framework Assembly “System.Net.Http 4.0.0.0”.

What I also do not understand is, that there is this weird binding redirect to 4.2.0.0 – where is that one coming from? To get around this one, I tried to add the following redirect to the app.config of the Service Fabric Service (which is consuming the class library):

But still no difference, I still get the error at runtime.

Anybody having a clue? Anybody having seen such issue?

Answer 1

The problem you're facing is related to Visual Studio, especially 2017 which is shipped with System.Net.Http v4.2.0.0. However, adopting the new way whereby any references should be done via NuGet, latest version of System.Net.Http which is 4.3.3 contains the dll version 4.1.1.2.

The problem is that VS at build time and at run time as well will ignore your reference and it will try to reference the DLL it knows about.

How to fix it:

• make sure that any references to System.Net.Http are done via NuGet
• Build time errors: change extension of System.Net.Http.dll (or move it somewhere else...basically get rid of it) that is shipped with VS 2017 (c:Program Files (x86)Microsoft Visual Studio2017ProfessionalMSBuildMicrosoftMicrosoft.NET.Build.Extensions et461lib); if you've got a different version then the path will slightly differ, not much though

• Runtime errors: add an assembly binding redirect

If you look online on google you'll find a few open issues with Microsoft about this, so hopefully they'll fix this in the future.

Hope this helps.

Update:

When looking at finding some permanent fixes for this issue to work on the build agents, noticed that if you migrate to the new NuGet PackageReference model (in .csproj not in packages.config) tends to work better. Here's a link to the guide on how to do this upgrade: https://docs.microsoft.com/en-us/nuget/reference/migrate-packages-config-to-package-reference