private void ShowNonprintableCharactersToolStripMenuItemClick(object sender, EventArgs e)
{
showNonprintableCharactersToolStripMenuItem.Checked = !showNonprintableCharactersToolStripMenuItem.Checked;
showNonPrintChars.Checked = showNonprintableCharactersToolStripMenuItem.Checked;
_internalFileViewer.ShowEOLMarkers = showNonprintableCharactersToolStripMenuItem.Checked;
_internalFileViewer.ShowSpaces = showNonprintableCharactersToolStripMenuItem.Checked;
_internalFileViewer.ShowTabs = showNonprintableCharactersToolStripMenuItem.Checked;
}