This code demonstrates adding, and restoring, the seventh Item in a WinForms ComboBox:
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
if (comboBox1.Items.Contains("Item 7"))
{
comboBox1.Items.RemoveAt(6);
}
else
{
comboBox1.Items.Insert(6, "Item7");
}
}
You'll have to store and keep track of which items you remove, and where they should be inserted when you need to restore them.
You should read the documentation on the ComboBox.ObjectCollection Class' 'Contains, 'RemoveAt, and 'Insert methods.