You get this error when running your application:
Parser Error: Could not load file or assembly 'System.Web.Abstractions, Version=3.5.0.0
This error occurs when your system is running Microsoft .NET Framework 3.5 without Service Pack 1 (SP1) or later installed.
Install Service Pack 1 (SP1) or later for .NET Framework 3.5..
Part IX: Troubleshooting Applications
Application Runs But No Data is Displayed