Could not load file or assembly 'System.Net.Http, Version=2.0.0.0 in MVC4 Web API

I had the same error while deploying previously converted (from .NET 4.5 to 4.0) web app on IIS 6.0.

In the web.config runtime section I've found

<dependentAssembly>    <assemblyIdentity name="System.Net.Http" publicKeyToken="b03f5f7f11d50a3a" culture="neutral"/>    <bindingRedirect oldVersion="0.0.0.0-4.0.0.0" newVersion="4.0.0.0"/></dependentAssembly>

which I've changed to

<dependentAssembly>    <assemblyIdentity name="System.Net.Http" publicKeyToken="b03f5f7f11d50a3a" culture="neutral"/>    <bindingRedirect oldVersion="0.0.0.0-1.0.0.0" newVersion="2.0.0.0"/></dependentAssembly>

Now works like charm.

I had the same problem with deployment my app to appharbor. The problem it does not support .NET 4.5 yet. What I did.

1. Switched my project to .NET 4.0 profile.
2. Uninstalled Web API NuGet package.
3. Installed Web API (Beta) NuGet package again.
4. Verified that .csproj file contains for ALL referenced assemblies, so it will always take it from Bin folder, instead of GAC.

Mine worked with:

Note the redirect of 1-4 to 2.0

<dependentAssembly>    <assemblyIdentity name="System.Net.Http" publicKeyToken="b03f5f7f11d50a3a"   culture="neutral"/>    <bindingRedirect oldVersion="0.0.0.0-4.0.0.0" newVersion="2.0.0.0"/></dependentAssembly>