Try Response.Redirect(mypage,false) redirect error

Hi forum, my code:
 
if (ValidateLogin("nguoidung", txtTaiKhoan.Value, txtMatKhau.Value) == true) Response.Redirect("default.aspx", false);//***** Code isn't Redirect

if i remove FALSE, try catch Ex: Unable to evaluate expression because the code is optimized or a native frame is on top of the call stack.
Help me, thanks forum

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