判断窗体是否被处置来决定是否再次显示

Public Function midchi(ByVal frmName As String) As Boolean
Dim chiFrm As Windows.Forms.Form
For Each chiFrm In Me.MdiChildren
If chiFrm.Name = frmName Then
If chiFrm.Visible Then
chiFrm.Activate()
Else
chiFrm.Show()
End If
Return True
End If
Next
Return False
End Function

Private Sub MenuItem7_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MenuItem7.Click
If midchi("frmComputer") Then
Exit Sub
End If
Dim frmCp As New frmComputer
frmCp.MdiParent = Me
frmCp.Show()
End Sub