title: How to call windows authentication programmatically in sharepoint?
body: <p>Here is my scenario. </p>
  
  <ul>
  <li><p>When anonymous user visits site collection's default site, custom login form panel is shown. This form is a webUserControl(.ascx file) that is embeded into page as webpart. </p></li>
  <li><p>Then user enters username and password. </p></li>
  <li><p>When submit button has been clicked, authentication will be handled by code behind of custom login form panel.</p></li>
  </ul>
  
  <p>Here is my question. How can I call SharePoint's authentication method with the username and password that is entered by user. Simply, I want users to login through my custom login form panel instead of  windows authentication window.</p>