private void button3_Click(object sender, EventArgs e)
{
ManageCustomers dBoard = new ManageCustomers();
this.Close();
dBoard.Show();
}
private void toolStripMenuItem21_Click(object sender, EventArgs e)
{
foreach (Form var in Application.OpenForms)
{
var.Hide();
}
ManageCustomers frm = new ManageCustomers();
frm.Show();
}