public void uC_Menu3_UC_Click_1(object sender, EventArgs e) { cg = new Forms.Changgui(); cg.TopLevel = false; cg.Dock = DockStyle.Fill; panel_main.Controls.RemoveAt(0); panel_main.Controls.Add(cg); um.BackgroundImage = Properties.Resources.a; um.FontColor = Color.FromArgb(204, 204, 204); uC_Menu3.BackgroundImage = Properties.Resources.a1; uC_Menu3.FontColor = Color.White; um = uC_Menu3; cg.Tag = sender; cg.Show(); }