private void btnMilkTea_Click(object sender, EventArgs e)
{
MilkTea mt = new MilkTea();
mt.TopLevel = false;
pnCategory.Controls.Clear();
pnCategory.Controls.Add(mt);
mt.FormBorderStyle = FormBorderStyle.None;
mt.Dock = DockStyle.Fill;
mt.Show();
}
void MenuMilktea()
{
MilkTea mt = new MilkTea();
mt.TopLevel = false;
pnCategory.Controls.Clear();
pnCategory.Controls.Add(mt);
mt.FormBorderStyle = FormBorderStyle.None;
mt.Dock = DockStyle.Fill;
mt.Show();
}