EntityFramework error: The provider did not return a ProviderManifest instance

Question

My project is using ASP.NET MVC4, in C# with Visual Studio 2012 for Web Express.

When compiling my project, I have the following error:

The pr

Answer 1

This happens because VS2012 does not support sql 2012 and above. Change the value of ProviderManifestToken to 2008

Answer 2

For me it was because when I used TeamCity to deply my site, it changed the web.config file.

It removed the connectionString and added debug=true to System.Web compilation

<system.web>
    <customErrors mode="Off" />
    <authentication mode="None" />
    <compilation debug="true" targetFramework="4.5.2" />
    <httpRuntime targetFramework="4.5.2" maxRequestLength="1048576" />
    <httpModules>
      <add name="ApplicationInsightsWebTracking" type="Microsoft.ApplicationInsights.Web.ApplicationInsightsHttpModule, Microsoft.AI.Web" />
    </httpModules>
  </system.web>

I manuel fixed the web.config file, and it now works for me again.