using System.Windows.Forms; using System.Collections.Generic; using System; public class Test { static void Main() { Application.Run(new MainForm()); } } class MainForm : Form { public MainForm() { WindowState = FormWindowState.Maximized; IsMdiContainer = true; Form frm = new Childform(); frm.MdiParent = this; frm.Show(); Form frm2 = new Childform(); frm2.MdiParent = this; frm2.Show(); frm2.Left = 2000; } } class Childform : Form { DataGridView grid; Control LastFocus = null; public Childform() { ToolStripContainer tc = new ToolStripContainer(); grid = new DataGridView(); grid.Columns.Add(new DataGridViewTextBoxColumn()); grid.EditMode = DataGridViewEditMode.EditOnEnter; grid.Top = 120; grid.Height = 300; Controls.Add(tc); tc.ContentPanel.Controls.Add(new MyUserControl()); tc.ContentPanel.Controls.Add(grid); } protected override void OnActivated(EventArgs e) { base.OnActivated(e); if (this.LastFocus != null) { grid.Focus(); this.LastFocus.Focus(); } } protected override void OnDeactivate(EventArgs e) { base.OnDeactivate(e); this.LastFocus = this.ActiveControl; while (LastFocus is IContainerControl) LastFocus = ((IContainerControl)LastFocus).ActiveControl; } } class MyUserControl : UserControl { internal MyUserControl() { Height = 100; Controls.Add(new TextBox()); } }