C#

using Microsoft.Win32;
...
string keyName=...;
string valueName=...;
object defaultValue=...;

object o=Registry.GetValue(keyName,valueName,defaultValue);

if (o!=null) {
    // Key does not exist
}
else {
    // Do something with key
}

private void RenameFolder(DirectoryInfo dir, string NewName)
{
    dir.MoveTo(Path.Combine(dir.Parent.FullName,NewName));
}

private void ButtonHandler(object sender, System.EventArgs e)
{
    if(sender == this.buttonAdd)
    {
        // do something
    }
    else if(sender == this.buttonModify)
    {
        // do something
    }
    else if(sender == this.buttonDelete)
    {
        // do something
    }
}

SASA_1 wrote:

I am assuming I create this function in the ADD form,...

AboutBox box = new AboutBox();
box.Show();