test.cs

private void RemoveAllSections(TextControl textControl)
{            
    // remove all sections
    for (int section = 2; section <= textControl.Sections.Count;)
    {
        // set the input position to the start of the section
        textControl.Select(textControl.Sections[section].Start - 2, 0);

        // add a new paragraph
        textControl.Selection.Text = "\r\n";

        // select the end of paragraph character
        textControl.Selection.Length = 1;

        // remove the paragraph
        textControl.Selection.Text = "";
    }
}