If you'd like to use Code Behind, may I suggest the following solution for an asp:button -
ASPX Page
<asp:Button ID="btnRecover" runat="server" Text="Recover" OnClick="btnRecover_Click" />
Code Behind
protected void btnRecover_Click(object sender, EventArgs e)
{
var recoveryId = Guid.Parse(lbRecovery.SelectedValue);
var url = string.Format("{0}?RecoveryId={1}", @"../Recovery.aspx", vehicleId);
// Response.Redirect(url); // Old way
Response.Write("<script> window.open( '" + url + "','_blank' ); </script>");
Response.End();
}