title: How to fire a custom method after OnSignIn with MS Identity Platform
body: <p>I have a Blazor .Net 5 app using Identity Platform authentication.  Out of the box this all works fine, however, I would like to fire my own methods after .Net/AzureAD does it thing, but I am not sure how to best do this.</p>
  <p>So the user clicks a &quot;sign in&quot; link, that targets @MicrosoftIdentity/Account/SignIn&quot;, MS takes over and handles everything, and return to the callbackPath &quot;/signin-oidc&quot; as per the instructions to set this up.  How can I get the following code to run immediately after this process completes?</p>
  <pre><code>MyCustomPostSignInLogic()
  {
      // All my code to run once, post sign in
  }
  </code></pre>
  <p>As an additional ability, is there also a way to intervene .Net automatically sigining the user in, despite them being authenticated?</p>
  <pre><code>MyCustomOverrideSignInLogic()
  {
     // run this code and perhaps decide not to authenticate a user, despite them successfully completing MS auth.  Maybe we have blacklisted a user, and despite them having a valid MS account, don't want them to specifically authenticate against our app.
  }
  </code></pre>