Here is a proper way to do it - inherit a class from native ComboBox and override OnDropDown to raise a custom DropDownOpening event first. If you anticipate loading to take considerable time, you can wrap your reload code into a construct like this

I recently had a Microsoft workshop session and became excited about parallel for/foreach/etc. There we got a solid 60% of efficiency. It means that whenever number of cores increases by 2x, performance is boosted by 1.6x.

I recently stumbled upon this problem in one of our company .NET projects. For some reason, project settings there were configured for Text comparison, rather than Binary. As a result, lower case strings were equal to upper case, which was discovered later when some bug in UI occured. There were three solutions available.