>>> Now the actual question: is there a way to add a SqlConnection object (or possibly another class, but implementing the proper interface) that is accessible by the VS IDE designer, I can see it on the design surface, use it at design time, and yet at runtime I want to be able to "replace" - or "attach" a connection obtained from another source to this object so that I don't keep connection strings in my source code (or rather, prevent the IDE from autogenerating this code)? <<<
I have dealt with this by adding adapters via the IDE. As you indicated, the IDE will generate additional connection objects. I just delete the extra ones and simply leave one. Then I modify the adapters to use the sole connection object. As for the actual command string -- I override the one in use in the IDE in code by getting it from the application config file. Hope this helps. Howard