MDI窗体的疑问，之前过两次均失败了，解，多谢了

MDI窗体的疑问，之前求助过两次均失败了，在线等解，谢谢了！
MDI主窗体为 MDIform 子窗体有两个 分别是form1和form2

想要得到的效果是： 当我点击form1的显示事件时判断form2是否已经打开 打开的话就关闭form2然后再打开form1

相同的当我点击form2的显示事件时，也会判断form1是否已经打开，如果打开的话就关闭form1，然后打开form2

以上求老鸟解答了，谢谢！~

[解决办法]
new form1 form2时
把一个全局引用传入
[解决办法]

VB.NET code

'添加两个菜单，下面对应菜单项Public Class mdi    '打开form1    Private Sub Form1ToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Form1ToolStripMenuItem.Click        For Each frm As Form In Application.OpenForms            If String.Compare("form2", frm.Name.ToString, True) = 0 Then                frm.Close()                Console.WriteLine(frm.Name & " 已经关闭")                Exit For            End If        Next        Form1.Show()        Console.WriteLine("现在打开" & Form1.Name)    End Sub    '打开form2    Private Sub Form2ToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Form2ToolStripMenuItem.Click        For Each frm As Form In Application.OpenForms            If String.Compare("form1", frm.Name.ToString, True) = 0 Then                frm.Close()                Console.WriteLine(frm.Name & " 已经关闭")                Exit For            End If        Next        Form2.Show()        Console.WriteLine("现在打开" & Form2.Name)    End SubEnd Class