运行时编译错误来自Microsoft.AspNet.WebApi.HelpPage版本4.0.30506

当我尝试使用版本4.0.30506(不幸的是我们现在绑定到此版本的ASP.NEt Web API)的Microsoft.AspNet.WebApi.HelpPage nuget包时,我收到以下错误.我使用的是Windows 7和.NET 4.5.

Compilation Error

Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately. 

Compiler Error Message: CS0012: The type 'System.Object' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Runtime, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.

Source Error:


Line 11: 
Line 12:     // Group APIs by controller
Line 13:     ILookup apiGroups = Model.ToLookup(api => api.ActionDescriptor.ControllerDescriptor.ControllerName);
Line 14: }
Line 15: 

据我所知,我有所有正确的参考资料.我已经尝试过寻找一个System.Runtime程序集,但我在我的系统上找不到它.我已将index语句添加到Index.cshtml的顶部,但没有任何影响.

@using System
@using System.Runtime

有什么原因造成这个错误吗？