title: Enable button after an item in ListBox is selected
body: <p>At the moment I'm using</p>
  
  <pre><code>&lt;asp:ListBox ID="UserListBox" runat="server" AutoPostBack="true" OnSelectedIndexChanged="UserListBox_SelectedIndexChanged"&gt;&lt;/asp:ListBox&gt;
  </code></pre>
  
  <p>the button is disabled by default and after the <code>OnSelectedIndexChanged</code> is fired I am executing this behind.</p>
  
  <pre><code>protected void UserListBox_SelectedIndexChanged(object sender, EventArgs e)
  {
      loginBtn.Enabled = true;
  }
  </code></pre>
  
  <p>This is causing the site to reload. I don't want that, instead I need javascript but I'm not familiar.  </p>