> The version you indicated to me "DayPilotProMvcTrial-8.3.5848.zip" was developed using the asp net mvc architecture and not asp net mvc5 as above.
The download package includes binaries for MVC 3, MVC 4 and MVC 5. It looks like you used the version for MVC4 by accident. You'll find the MVC 5 version in "Binary/Mvc5" folder.
> However, the percent field in the gantt chart does not show the value we reported inside the OnBeforeTaskRender method for the PercentComplete property.
You are right. This should be fixed now in build 5849:
http://mvc.daypilot.org/sandbox/
> Error 1 The assembly 'DayPilot.Web.Mvc, Version = 8.3.5848.0, Culture = neutral, PublicKeyToken = b8d928e6588028e4' uses 'System.Web.Mvc, Version = 4.0.0.1, Culture = neutral, PublicKeyToken = 31bf3856ad364e35', which owns A newer version than the assembly 'System.Web.Mvc, Version = 4.0.0.0, Culture = neutral, PublicKeyToken = 31bf3856ad364e35' used as reference
This happens because your system has MVC 4 version installed and it's an older version which has security bugs. Microsoft released a fix and in order to force users to upgrade it they changed the reference version from 4.0.0.0 to 4.0.0.1. It needs to be updated to the latest version. See also:
https://blogs.msdn.microsoft.com/webdev/2014/10/16/microsoft-asp-net-mvc-security-update-ms14-059-broke-my-build/