Today we started getting an error from three web applications. Two were web services and one was an ASP.NET MVC website. The error was:
Could not load file or assembly ‘System.Net.Http, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a’ or one of its dependencies. The located assembly’s manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
The error was occurring on this standard line in the global.asax file:
WebApiConfig.Register(GlobalConfiguration.Configuration)
Looking at the trace statements on the error page, there was a mention of a binding redirect, which I recall seeing in the web.config of the site. That section in the web config looked like:
<runtime>
<assemblybinding xmlns="urn:schemas-microsoft-com:asm.v1">
<dependentassembly>
<assemblyidentity culture="neutral" publickeytoken="b03f5f7f11d50a3a" name="System.Net.Http">
<bindingredirect newversion="2.2.29.0" oldversion="0.0.0.0-2.2.29.0">
</bindingredirect>
</assemblyidentity>
</dependentassembly>
</assemblybinding>
</runtime>
This config block had been in place since December, 2015. The block seems to have been added by a NuGet package at the same time, possibly with a Framework version upgrade.
However it originally ended up there, removing the config block allowed the sites to launch again. It’s unknown why this started happening after a Visual Studio upgrade.