Use the Aspose.GIS for .NET library to implement the TopoJSON viewer.
Aspose.GIS for .NET / C# presents you online free the “TopoJSON Viewer” application, where you may to investigate the functionality and quality it works.
Code sample - TopoJSON Viewer
The following code snippet shows you how to implement TopoJSON Viewer. The below code create an image map using a TopoJSON layer. If you specify a spatial reference system for the map, all loaded layers will be converted to it. The sample uses the specified style to draw lines. The library also has styles for points, lines, and surfaces.
This sample show general possibilities. Aspose.GIS for .NET has wide features to render maps.
Platform - .NET / C#
We supports Framework 4.7 or later under Windows, and .NET Core 2.0 or later under Windows or Linux