如何使浏览器始终提示客户端证书？

Question

我已经设置了IIS服务器以要求客户端证书。但浏览器从不询问用户，即使IE已启用“不提示客户端证书选择时，它也直接发送客户端证书信息”

我的代码或IIS中有什么事吗？

public partial class Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {

        Welcome.Text = "Hello, " + Context.User.Identity.Name;

        string userName;
        userName = User.Identity.Name;

        HttpClientCertificate cert = Request.ClientCertificate;
        if (cert.IsPresent)
            certDataLabel.Text = cert.Issuer;
        else
            certDataLabel.Text = "No certificate was found.";
    }

    protected void Signout_Click(object sender, EventArgs e)
    {
        FormsAuthentication.SignOut();
        Response.Redirect("Logon.aspx");
    }

}