private void btnAdd_MouseClick(object sender, MouseEventArgs e)
{
var newDateDue = dtPicker.Value;
var addDeadline = cbAddDate.Checked;
var newText = rtBox.Text;
controller.AddNewTodo(newDateDue, addDeadline, newText);
dtPicker.Value = DateTime.Now;
cbAddDate.Checked = false;
rtBox.Text = "";
controller.todoEnt.SaveChanges();
refreshParentForm.Invoke();
}