private void ShowAllBooksToolStripMenuItem_Click(object sender, EventArgs e)
{
this.Hide();
ShowAllBooks sab = new ShowAllBooks();
sab.Show();
}
private void btnShowAllBooks_Click(object sender, EventArgs e)
{
ShowAllBooks showAllbooks = new ShowAllBooks();
this.Hide();
showAllbooks.ShowDialog();
this.Show();
}