tabControl1的selectclick事件中处理。
TabPage pages = tabControl1.SelectedTab;
//// 货物打包
if (pages.Name == this.tabPage1.Name)
{
var frm = new Form2();
frm.TopLevel = false;
frm.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
frm.Dock = DockStyle.Fill;
frm.Show();
this.tabPage1.Controls.Add(frm);
}