I'm seeing a lot of confusion about this.
Microsoft has OWIN client libraries for OpenID Connect / OAuth2.
It also has ADAL - Active Directory Authentication Library (used mainly for native devices).
Both implement the protocols so you would think that you can use these to hook up to any server that implements OpenID Connect / OAuth.
Except that you would be wrong.
OAuth is notorious for incompatibility so you can't really mix and match.
These libraries are aimed at a specific use case i.e. the server is either Azure AD or ADFS.
In addition, the profile is hybrid flow so if your server doesn't implement that you are already out of luck,
Which is not to say that it won't work in some cases.
e.g. IdentityServer 3 does implement the hybrid flow.
Refer : IdentityServer : The WebApp-OpenIDConnect-DotNet Azure AD sample.
Here I show how to use the OWIN library to connect to IdentityServer 3. As you can see, I had to make some alterations.