I believe that you have enabled Break when Exception is Thrown
option in Visual Studio Debug menu
is information how to enable it and you can use the same process to disable this behaviour.
In general this should happen only when you are debugging with Visual Studio
attached to the process.
This is behaviour specific for Visual Studio
and you can experience the same effect using any method that throws exception when this option is enabled.
Hope that helps you avoid this inconvenience.
All the best,
the Telerik team
Telerik OpenAccess ORM Meets ASP.NET Web API. Read more.