Over the past year I've reviewed a few products from Red Gate - SQL

Compare,  Data

Compare, and SQL

Comparison and Synchronization Toolkit, all fine products! If you buy their

"bundle" you also

get a smaller app called COMCompare. I thought it might be useful to take a quick look at what it does

and how it might be a helpful tool to have around.

It's a product well named. It compares any two COM objects (dll, ocx, olb,

tlb) that contain a type library. It won't open a "standard" dll that

exports functions. Just a note, I'm not aware of a comparable product for those

types of dll's but you can at least see the exported functions using the Dependency

Walker tool that ships with Visual Studio Enterprise Edition.

Using it is simple. Select two COM files and click ok. For this article I put

together a very basic COM dll consisting of a person class, then copied the

entire project to a new folder and changed the class by adding an event,

changing a data type, etc.

Clicking ok gave me the following display:

I know that's chopped off a bit, hopefully it will do! Let's talk about what

we can tell from the comparison. On line three of the grid you can see that

there is a property called FullName that is readonly (ro) that doesn't exist in

the object on the right. Skip down to the line about DateOfBirth and you can see

that the properties don't match - in the left object it's typed as a string, and

in the right it's a date. Further down you can see where I added the

HasTooManyFingers event to the left object.

Now unfortunately you can't use the utility to generate 'sync' code the way

you can with SQL Compare or Data Compare, but after all we're comparing compiled

code, not source!

So why would you need this utility? While I think it's targeted more towards

developers than DBA's, it's not so rare that those roles

merge a bit. DLL incompatibilities abound and they are often subtle. I'm able to

resolve most of them by checking the version information in the dll/ocx, it's

usually...but not always...accurate. Having a tool that will let you do a

quick comparison is a lot easier than trying to flip back and forth between two

copies of VB trying to compare settings from the Object Browser.

Is it the first SQL tool you should buy? Of course not. But considering the

price of the bundle which includes it plus SQL Compare plus Data Compare, why

not just buy the bundle and have it when you need it? Got questions or comments?

Post a message in the attached discussion area and I'll normally respond the

same day.