It looks you misunderstand this problem, the winforms map is a map control:
a. It can render the offline data, which is provided by the user
b. It can render the online base map or other online data for example WMS etc. It's provided by the 3rd part service
That means the map don't contains data itself. Your target is shows the house border on OpenStreetMap base map.
The solution is:
a. You have the offline house border data, then you can render it above the base layer
b. The 3rd part online data contains house border
In this case, it looks the OpenStreetMap library tile image don't have house border. That means if you have to render hte house border, you should want to choose Google map as base map instead of OpenStreetMap.
Wish that's helpful.