TransparencyKey Property on Forms

I would like to swith my form background transparency with Visual C# in a Windows Forms Application.

I used

BackColor = Color.White;
TransparencyKey = Color.White;

Now I want to switch back to "not transparent". How can I accomplish that? Just switching the BackColor makes the elements on the form look strange and it feels ugly. I guess there is a way to reset the property.

this is the original value:

this.TransparencyKey = Color.Empty;

You could set this, and then nothing will be transparent.

How about storing the previous values of BackColor and TransparencyKey in local variables, and restoring them when you want to revert to non-transparent? For instance:

private Color _oldBG;
private Color _oldTPKey;

private void MakeTransparent() {
    _oldBG = BackColor;
    _oldTPKey = TransparencyKey;
    BackColor = Color.White;
    TransparencyKey = Color.White;
}

private void MakeNonTransparent() {
    BackColor = _oldBG;
    TransparencyKey = _oldTPKey;
}