void contextMenu_Opening(object sender, CancelEventArgs e)
{
bool enable = this._scintilla.Selection.Length > 0;
this.copyToolStripMenuItem.Enabled = enable;
this.cutToolStripMenuItem.Enabled = enable;
this.deleteToolStripMenuItem.Enabled = enable;
this.commentToolStripMenuItem.Enabled = enable;
this.addToAutoCompleteToolStripMenuItem.Enabled = enable;
}