private void contextMenuStrip_Opening(object sender, CancelEventArgs e)
{
TreeNode selectedNode = treeFolders.SelectedNode;
if (selectedNode == null)
{
createFolderToolStripMenuItem.Enabled = true;
deleteFolderToolStripMenuItem.Enabled = false;
}
else
{
createFolderToolStripMenuItem.Enabled = true;
deleteFolderToolStripMenuItem.Enabled = true;
}
}