title: Uncheck Select All Checkbox when one checkbox is Unchecked C# in windows form
body: <p>I have a checkbox when you click on it it select all checkbox the problem here that when unchecked any check box checked didn't remove from select all I tried this code:</p>
  
  <pre><code>private void checkBox1_CheckedChanged(object sender, EventArgs e)
  {
      if (checkBox1.Checked == false) 
          checkBox9.Checked = false;
  }
  </code></pre>
  
  <p>but when i checked any check box it remove all checkbox i want to unchecked select all only not all checkbox</p>