Simple answer is that you cannot detect and internet connection type, and furthermore the connection type (or medium used by internet connection) of a client.
What?
You should know... ASP.NET passes down only the HTML markup of your application; along with other resources such as images, JavaScript files and CSS style sheets. It has no idea what type of medium a user would be using; wireless internet or a wired. Although using some values of the request headers, it can check for whether it is a mobile device or a computer (or using CSS3 whether a printed page).
But you cannot have a control over the client's machine. You cannot see the transport layer or the physical layer (these are used in
Networking as layers[
^] in the
OSI Model[
^]). So, only if you design a software to have a control over the hardware only then you can determine what sort of medium is being used. Because I don't think .NET framework supports such a capability and power for developers to determine network and other devices-based connections. I have never seen anything like that in
System.Net
namespaces.