C# 父窗口应用，调用子窗口

        private ChildFrm myChildFrm; //定义子窗口对象
        private void button1_Click(object sender, EventArgs e)
        {
            if(myChildFrm == null || myChildFrm.IsDisposed)
            {  
            myChildFrm = new ChildFrm();
            }
            this.IsMdiContainer = true;   
            myChildFrm.MdiParent = this; //建立父子关系
            myChildFrm.Show(); //显示子窗口
            myChildFrm.Focus(); //子窗口获得焦点

        }