title: What is different among this.ActiveControl = XControl , XControl.Focus() in winforms?
body: <p>I work on a C# Winform project. </p>
  
  <p>I don't know what is different among </p>
  
  <ol>
  <li><code>this.ActiveControl = XControl;</code></li>
  <li><code>XControl.Focus();</code></li>
  </ol>
  
  <p>Sometimes <code>XControl.Focus()</code> do not work and I have to set <code>this.ActiveControl = XControl</code>. I don't know why it happens. I'm confused, can anyone help me?</p>