You may see this JavaScript exception in the browser console if you use the JavaScript files from DayPilot Pro for ASP.NET WebForms directly. In ASP.NET WebForms, it is necessary to use the controls by including the ASP.NET controls (e.g. DayPilotScheduler) in a WebForms page.

Licensing Restrictions

Please note that using the JavaScript files (e.g. scheduler.js, scheduler.src.js) from DayPilot Pro for ASP.NET WebForms in a standalone mode (outside of ASP.NET controls from DayPilot.dll) requires a DayPilot Pro for JavaScript license. The standalone usage of the JavaScript files has been limited by the license since the introduction of DayPilot Pro for JavaScript in 2013. See also the license agreement for details.