Build windows application for Google maps

Using .net C# for windows application and Google API, it is required to write and supply the source code to get the polygonal of the surrounding building from a specific point in a given radius.

1. User input one coordinates and a circular radius.
2. You will find all the buildings in this circular.
3. For each building, return the building roof height and the polygon of the building boundary.
4. see the attached pic as a reference.

Required .net version is 4.0, and no external dll/library is allowed without a previous approval from our side.