Porting to newest bug tracker.

https://visualstudio.uservoice.com/forums/121579-visual-studio/suggestions/6264363-add-support-for-alpn-to-system-net-security-sslstr

https://connect.microsoft.com/VisualStudio/feedback/details/812003/system-net-security-sslstream-needs-support-for-alpn-to-negotiate-spdy-http2-connections

Microsoft drove the HTTP/2 working group to adopt the ALPN TLS Extension for use in negotiating HTTP/2 connections. It succeeded. SChannel got ALPN support in the Windows 8 timeframe.

.NET's SslStream class does not have ALPN support, preventing low-level socket clients (like Fiddler) from sending ALPN tokens to servers during TLS handshaking, in turn blocking support of the HTTP/2 protocol.

The code change to SslStream is probably a dozen lines at worst. The current workaround for those blocked by this shortcoming is to take on a massive security risk and ship either BouncyCastle or OpenSSL (or re-wrap SChannel, I guess).