To reproduce:
1. Create a project
2. Add a Telerik form
3. Add a RadCommandBar
4. Add some buttons
5. Debug application
(forget you are running application)
6. Click on add button on command bar. As a result, Visual studio Crashes.

Note: if you perform the same steps with RadRibbonBar a message is shown that the file can't be modified  while debugging. Please refer to the attached screenshot.