How to prompt the default windows credentials dialog form for internet proxy in .NET?

My .NET app uses a WebService and, in some clients, I am getting HTTP 407 (proxy authentication required). So I need to ask the user to input his user/password credentials.

So, how to use t开发者_JS百科he default Windows dialog? (see below)

Is it possible in .NET? Or will I need to build my own custom form?

Internet Proxy Credentials Dialog http://grab.by/23II

Have a look here

It contains a class that will get the Credential Dialog and an example of how to use it.