Debugging Control Add-ins

If an error occurs, when running a page, where a custom control add-in was added, then it’s often not easy to find the error reason. Typical error message: Exception has been thrown by the target of an invocation.

An expert method to analyse add-ins is using Visual Studio.
For that run visual studio and goto menu “debug”, menu item “attach to process …”. in the following dialog select Microsoft.Dynamics.Nav.Client.exe.


Then start the nav windows client (RTC), open the page, which contains the field with the control-addin and start the according action. After that, the error is shown in visual studio at the exact position, where the error occurs (debug mode).
In most cases there is for sure an unhandled exception. Edit the c# source file, fix the code and add at this position a better exception handling to get a better speaking exception message.

Also helpful for analysing purposes is to develope a logging mechanism, e.g. write eventlog entries.

Error, when creating an instance of a .net class

Following error can occur, when creating an instance of a .net class in C/AL:



  • If the assembly is used on client side (property RunOnClient=True), then the assembly was not copied to the local Add-ins Folder of the RTC Client. To copy the assembly into this folder you need in most cases Admin rights. So, check that first.
  • If the assembly is used on server sideĀ (property RunOnClient=False), then there might be a version conflict between the assembly file located in the Add-ins Folder of the Nav Service and the used version in the C/AL Code. That can easy occur after installing Updates. So update the code and restart the nav service.
  • Missing System permission: That means, that the assembly was copied from the web or from a computer outside the local network to a target computer/server with windows server OS. Then, the assembly is automatically blocked by the system.