The only way to get a .NET app and AEM working is to perform REST operation from the .NET app to AEM. You can certainly store images in AEM and then reference them in the .NET site via an URL. But other then using Restful operations - ie - GET or POSTs to AEM, or referencing images, there is not much you can do. You cannot build an AEM component and consume that component in a .NET app.
Here is an older article that shows use of .NET and AEM via a POST operation:
Scott's Digital Community: Submitting .NET client application data to the Adobe CQ JCR
