C#

'Declare a Form global boolean to keep the ItemChecked event from being called in an infinite loop
Dim bFirstChange as Boolean = True

Private Sub Listview1_ItemChecked(ByVal sender As System.Object, ByVal e As System.Windows.Forms.ItemCheckedEventArgs) Handles Listview1.ItemChecked
    If ((ModifierKeys = Keys.Control) Or (ModifierKeys = Keys.Shift)) Then
        If (bFirstChange) Then
            bFirstChange = False
            e.Item.Checked = Not e.Item.Checked
        Else
            bFirstChange = True
        End If
        Exit Sub
    End If
    'Accentuate that the row is checked
    If (e.Item.Checked) Then
        e.Item.SubItems(0).Text = "+"
        e.Item.BackColor = Color.LightYellow
    Else
        e.Item.SubItems(0).Text = "-"
        e.Item.BackColor = Color.White
    End If
End Sub

Private Sub ListView1_ItemCheck(ByVal sender As Object, ByVal e As System.Windows.Forms.ItemCheckEventArgs) Handles ListView1.ItemCheck
  If (ModifierKeys And (Keys.Shift Or Keys.Control)) <> 0 Then e.NewValue = e.CurrentValue
End Sub

private: System::Void listView1_ItemCheck(System::Object^  sender, System::Windows::Forms::ItemCheckEventArgs^  e)
		 {
			 if( (ModifierKeys == Keys::Control) || (ModifierKeys == Keys::Shift) )
			 {
				 e->NewValue = e->CurrentValue;
			 }
		 }

if (Control.ModifierKeys == Keys.Shift || Control.ModifierKeys == Keys.Control)
{
    e.NewValue = e.CurrentValue;
}

if( (Control.ModifierKeys & (Keys.Shift | Keys.Control)) )
{
    e.NewValue = e.CurrentValue;
}