title: How To Configure Twitter External Authentication in ASP.NET Core 3.0 Identity
body: <p>I've added the Twitter external sign-in NuGet package to my ASP.NET Core 3 app as outlined on the following Microsoft page.</p>
  <p><a href="https://docs.microsoft.com/en-us/aspnet/core/security/authentication/social/twitter-logins?view=aspnetcore-3.1" rel="nofollow noreferrer">Twitter external sign-in setup with ASP.NET Core</a></p>
  <p>This is a screenshot of a portion of the doc:
  <a href="https://i.stack.imgur.com/dMTlG.png" rel="nofollow noreferrer">Configure Twitter Authentication DefaultScheme</a></p>
  <p>Now I'm trying to access and modify the /signin-twitter default callback that was set up automatically by the NuGet installation. Also, I want to setup my own DefaultScheme to process authentications.</p>
  <p>I have 2 questions.</p>
  <ol>
  <li><p>How do I access and modify the code in the /signin-twitter default callback that is set up automatically by the Twitter authentication NuGet package? There is no /signin-twitter file or component in the application file structure. And a search does not find &quot;signin-twitter&quot; text mentioned in any file. Where is the /signin-twitter code located?</p>
  </li>
  <li><p>In the attached screenshot, you'll see the verbiage that says &quot;The AddAuthentication(String) overload sets the DefaultScheme property&quot;. But the doc has no example that shows how to do this. How do I set up my own DefaultScheme to process authentications using AddAuthentication(String)? And what type of code file should it be?</p>
  </li>
  </ol>
  <p>Any assistance will be greatly appreciated. Thank you in advance.</p>