By Adam Nagy
You may want to create command dialogs or palettes that look just like Inventor's, e.g. like the one the Extrude command has.
Unfortunately, there is no direct way to do that; Inventor API does not provide a way to reuse components or customize existing dialogs.
Also, the icons being used are spread across different resource dll's so it could be difficult to find them. The easiest way to create a dialog similar to an Inventor command's is to get a screenshot of the UI that you are interested in and then recreate from that the png's needed for your buttons.
There is a sample in the SDK that does that: "C:\Users\Public\Documents\Autodesk\Inventor 2015\SDK\DeveloperTools\Samples\VCSharp.NET\AddIns\CustomCommand"
I have updated it to use the latest UI look, inc. making the entity selection button's arrow white once the selection has been accomplished, use png's instead of ico's, and added a nice command icon as well - Download CustomCommand2015