Set VBScript Err.Number by throwing .NET exception in c# COM object

[Kevinst]

Hello,

I have a c# com object that exposes several methods.
This com object is to be used in vbscripts as well as vba scripts.

In my application error handling is done by throwing different types of custom exceptions. The problem is that when theses exceptions are caught by the vbscript the type of the exception is unknown.

Therefore I would need Err.Number to determine what kind of exception was thrown. Unfortunately I have not been able to figure out how that works.

For some reason ExternalException does not do the trick.

Simple example:

COM object:

[ComVisible(true)]
public class MyClass
{
public void Test()
{
throw new MyTimeoutException() //MyTimeoutException somehow sets Err.Code to 123
}
}
 

vbscript:

Dim k
set k = CreateObject("ns.MyClass")
on error resume next
k.Test
 
if err.number = 123 then
    MsgBox "Crap. Operation timed out."
end if
 
set k = nothing
 

I have been googeling for hours without any kind of success.

Kevin

[Plater]

I would hazzard a guess that maybe you need to throw a COMException?
I am not really sure where the error code for vbscript gets pulled from

[Kevinst]

Thought the same thing.

No success either.

[Kevinst]

Solution:
Either derive your custom exception from ApplicationException and set the HResult Property or throw an exception using Marshal.ThrowExceptionForHR.

Attention: The HResults have to be negative values.