Form1(MDIParent)

public partial class Form1 : Form{    public interface ITools    {        ToolStrip CipherToolStrip        {            get;        }    }    public Form1()    {        InitializeComponent();    }    private void newToolStripMenuItem_Click(object sender, EventArgs e)    {        Form2 f2 = new Form2();        f2.MdiParent = this;        f2.Show();    }    private void Form1_MdiChildActivate(object sender, EventArgs e)    {        ToolStripManager.RevertMerge(MDIParent);        if (this.ActiveMdiChild != null)        {            if ((ActiveMdiChild as ITools).CipherToolStrip != null)            {                ToolStripManager.Merge((ActiveMdiChild as ITools).CipherToolStrip, MDIParent);            }        }        if (MDIParent.Items.Count > 0)            MDIParent.Visible = true;        else            MDIParent.Visible = false;    }}

Form2(MDIChild)

public partial class Form2 : Form, Form1.ITools{    public ToolStrip CipherToolStrip    {        get        {            return MDIChild;        }    }    public Form2()    {        InitializeComponent();    }    private void Form2_Load(object sender, EventArgs e)    {        MDIChild.Visible = false;        ControlBox = false;    }}

通过设置 MergeAction 和 MergeIndex 可以修改合并的方式与位置。

  

运行结果如下：