I would suggest buying a basic C# book and reading it, instead of guessing. For this code to work, you'd have to define controls called checked and unchecked, so that they could be compared. You should also consider posting the full error message to us, and perhaps reading it first.
if (checkbox1.Checked)
{
}
else
{
}
Also, don't use your email address as your user id, unless you like spam.