This document describes how to register a Bing Maps account and create a key to be able to use this map provider in your application.
If you connect your MapControl to Bing Maps using the BingMapDataProvider and don't specify the valid Bing Maps key, you will get the following error:
"The specified Bing Maps key is invalid. To create a developer account, refer to https://www.microsoft.com/en-us/maps/create-a-bing-maps-key"
This error is shown in the image below.
The error message suggests visiting the official Microsoft web page devoted to Bing Maps. This page contains links to web resources, which are useful for map application developers. The page also suggests that you create a new account and get a developer key for it.