Difference in capabilities between Add-Ins and COM Extensions?

DominicRorke

Hi, I'm trying to work out what the difference is between Add-Ins and classic COM based extension models in terms of the capability of each approach, and when to use one approach instead of the other?

It is clear to see that Add-Ins have a number of benefits in terms of the speed of development, ease of distribution and maintenance etc, and it is useful to have the option of the Add-In distribution model, but is there any limit to the complexity of what can be developed with Add-Ins as opposed to COM registered extensions?

The ESRI 9.4 topic 'Roadmap for ArcGIS desktop customisation' seems to pitch Add-Ins as being a lighter weight development option for providing small customisations, whilst COM registered extensions requiring installers are pitched as "Custom components to add new functionality" (sounds like these can do more complex stuff); but surely the same custom code can be used and developed, and ArcObjects extended to the same extent and complexity with either approach?  Is it actually the case that both development models are as capable as each other?

Is it that there are benefits to the COM extension approach when multiple developers are working on an extension, as opposed to the Add-In model?

Is it that the COM extension is the clear choice when developing an extension on a commercial basis, as extension licensing and the requirement to have an administrator control on application distribution make COM extensions more appropriate for this scenario?

How does one decide which approach is most suitable, as the boundary between the two approaches appears to be rather blurred?

If you could provide some clarity on this it would be appreciated.

Many thanks,

Dominic

Anonymous User

I have an existing extension that implements ILayer to retrieve info on the layers in the TOC - is this possible with an Add-in?

No, its not possible with an add-in at 10.0. You cannot implement an interface in the add-in class. You can write it and the code will compile but internally the cast to the interface will fail and nothing will happen. You will be able to do this at 10.1 however. The restriction with component categories still applies (ie. you cant specify any -- except for some editor construction tools at 10.1).