Public Sub mniCopy_Click(ByVal sender As Object, _
   ByVal e As System.EventArgs) Handles mniCopy.Click

   ' Determine the active child form.
   Dim activeChild As Form = Me.ActiveMDIChild

   ' If there is an active child form, find the active control, which
   ' in this example should be a RichTextBox.
   If (Not activeChild Is Nothing) Then
      Try
         Dim theBox As RichTextBox = _
         Ctype(activeChild.ActiveControl, RichTextBox)
         If (Not theBox Is Nothing) Then
            ' Put selected text on Clipboard.
            Clipboard.SetDataObject(theBox.SelectedText)
         End If
      Catch
         MessageBox.Show("You need to select a RichTextBox.")
      End Try
   End If
End Sub

protected void mniCopy_Click (object sender, System.EventArgs e)
{
   // Determine the active child form.
   Form activeChild = this.ActiveMdiChild;

   // If there is an active child form, find the active control, which
   // in this example should be a RichTextBox.
   if (activeChild != null)
   {  
      try
      {
         RichTextBox theBox = (RichTextBox)activeChild.ActiveControl;
         if (theBox != null)
         {
            // Put the selected text on the Clipboard.
            Clipboard.SetDataObject(theBox.SelectedText);
            
         }
      }
      catch
      {
         MessageBox.Show("You need to select a RichTextBox.");
      }
   }
}

private void menuItem5_Click(System.Object sender, System.EventArgs e) 
{
   // Determine the active child form.
   Form activeChild = this.get_ActiveMdiChild();
      
   // If there is an active child form, find the active control, which
   // in this example should be a RichTextBox.
   if ( activeChild  != null  ) 
   {
      try 
      {
         RichTextBox theBox = ((RichTextBox)(activeChild.get_ActiveControl()));
         if ( theBox  != null  ) 
         {
            // Create a new instance of the DataObject interface.
            IDataObject data = Clipboard.GetDataObject();
            // If the data is text, then set the text of the 
            // RichTextBox to the text in the clipboard.
            if (data.GetDataPresent(DataFormats.Text)) 
            {
               theBox.set_SelectedText(data.GetData(DataFormats.Text).ToString());
            }
         }
      }
      catch(System.Exception exp)
      {
         
         MessageBox.Show("You need to select a RichTextBox.");
      }
   }
}