C#, VB.NET como abrir um form só uma vez em ambiente MDI

C#

frmSysFuncionarios xForm; 
  foreach (Form childForm in this.MdiChildren) 
  { 
if (childForm.GetType() == typeof(frmSysFuncionarios)) 
       { 
            childForm.Focus(); 
            return; 
        } 
   } 
xForm = new frmSysFuncionarios(); 
xForm.MdiParent = this; 
xForm.Show()

VB.NET

Dim xForm As frmSysFuncionarios 
For Each childForm As Form In Me.MdiChildren 
    If childForm.[GetType]() = GetType(frmSysFuncionarios) Then 
        childForm.Focus() 
        Return 
    End If 
Next 
xForm = New frmSysFuncionarios() 
xForm.MdiParent = Me 
xForm.Show()