Could not load file or assembly 'WebGrease' or one of its dependencies

I had the same issue.

This was resolved by

1) running the Package Manager Console

2) in Console, type: 'Install-Package Microsoft.AspNet.Web.Optimization'

which resolved all the incorrect dependencies.

I had to run Update-Package -Reinstall Microsoft.AspNet.Web.Optimization

That updated my web.config and all references

Check the contents of runtime/assemblyBinding section in web.config. I found incorrectly registered dependentAssembly elements after installing Kendo UI package. I manually removed duplicates and the problem disappeared.

Replace:

<assemblyIdentity name="System.Web.WebPages" publicKeyToken="31bf3856ad364e35" /> <bindingRedirect oldVersion="1.0.0.0-2.0.0.0" newVersion="2.0.0.0" />

For:

 <assemblyIdentity name="WebGrease" publicKeyToken="31bf3856ad364e35" />
    <bindingRedirect oldVersion="1.0.0.0-1.3.0.0" newVersion="1.3.0.0" />