C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
using System.Security.Principal;
using System.Security.Permissions;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.Windows.Forms;
using System.Diagnostics;
using System.IO;
using System.Security;
using System.ComponentModel;

namespace SmartCardApp
{
   
       
       

    public class SmartCard
    {
      
        internal static int CertCredential = 1;
                      
        [DllImport("advapi32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        public static extern bool CredMarshalCredential(
            int credType,
            IntPtr credential,
            out IntPtr marshaledCredential
            );
      

        [DllImport("user32.dll")]
        private static extern IntPtr GetDC(IntPtr hWnd);
        [StructLayout(LayoutKind.Sequential)]
        internal struct CERT_CREDENTIAL_INFO
        {
            public uint cbSize;

            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)]
            public byte[] rgbHashOfCert;
        }


        public static string pin = null;
        public static X509Certificate2 cert = null;
        public struct UserLoginInfo
        {
            public string domain;
            public string username;
            public SecureString password;
        }
        public void SmartCardLogon()
        {
            //First Get the Certificate
            cert = GetClientCertificate();
            //Create a pin logon form
            Form login = new Form();
            login.Height = 100;
            login.Width = 100;
            login.MaximizeBox = false;
            login.MinimizeBox = false;
            login.ControlBox = false;
            login.Name = "frmCaCLogin";
            login.Text = "Enter Pin";
            TextBox TextBox1 = new TextBox();
            TextBox1.Name = "txtCaCLogin";
            TextBox1.PasswordChar = '*';
            
            login.Controls.Add(TextBox1);
            Button b = new Button();
            b.FlatStyle = FlatStyle.Flat;
            b.Text = "Login";
            b.Name = "butCacLogin";
            b.Click += new EventHandler(b_Click);
          
            login.Controls.Add(b);
            login.Controls["butCacLogin"].Top += 20;
            login.TopMost = true;
            login.ShowDialog();



        }

        void b_Click(object sender, EventArgs e)
        {
            //Retrive the pin from the txt filed you added to the created form
            pin = Application.OpenForms["frmCaCLogin"].Controls["txtCaCLogin"].Text;
            //just hides the form
            Application.OpenForms["frmCaCLogin"].Hide();
            //
           
        
            if (cert != null)
            {
                //This returns the cert and pin as a username and password that can be used with processstartinfo
                UserLoginInfo user = Login(cert);
                ProcessStartInfo psi = new ProcessStartInfo();
                psi.FileName = Application.ExecutablePath;
                psi.UserName = user.username;
                psi.Password = user.password;
                psi.UseShellExecute = false;
                Process.Start(psi);
                Application.Exit();

            }
        }

        public UserLoginInfo Login(X509Certificate2 cert)
        {
            UserLoginInfo uli = new UserLoginInfo();

            CERT_CREDENTIAL_INFO certInfo =
                 new CERT_CREDENTIAL_INFO();
            certInfo.cbSize = (uint)Marshal.SizeOf(typeof(CERT_CREDENTIAL_INFO));
            // certCredential.Certificate is an instance of the X509Certificate2 class.
            certInfo.rgbHashOfCert = cert.GetCertHash();

            int size = Marshal.SizeOf(certInfo);
            IntPtr pCertInfo = Marshal.AllocHGlobal(size);
            Marshal.StructureToPtr(certInfo, pCertInfo, false);

            IntPtr marshaledCredential = IntPtr.Zero;
            bool result =
               CredMarshalCredential(CertCredential,
                                pCertInfo,
                                out marshaledCredential);
            string domainName = string.Empty;
            string userName = string.Empty;
            string password = string.Empty;
            if (result)
            {
                // we need to do this here, before we free marshaledCredential
                domainName = String.Empty;
                userName = Marshal.PtrToStringUni(marshaledCredential);
                password = pin;
            }
            SecureString sc = new SecureString();
            foreach (char c in pin)
            {
                sc.AppendChar(c);
            }

            uli.domain = Environment.UserDomainName;
            uli.username = userName;
            uli.password = sc;

           
            return uli;
        }

        
        public static X509Certificate2 GetClientCertificate()
        {
            WindowsImpersonationContext impersonationContext = null;
            IntPtr ptr = IntPtr.Zero;
            X509Certificate2 certificate = null;
            X509Certificate t = null;
            var store = new X509Store(StoreName.My, StoreLocation.CurrentUser);
            try
            {
                store.Open(OpenFlags.ReadOnly | OpenFlags.OpenExistingOnly);
                // Nothing to do if no cert found.
                if (store.Certificates != null && store.Certificates.Count > 0)
                {
                    if (store.Certificates.Count == 1)
                    {
                        // Return the certificate present.
                        certificate = store.Certificates[0];
                    }
                    else
                    {
                        // Request the user to select a certificate 

                        var certificates = X509Certificate2UI.SelectFromCollection(store.Certificates, "Digital Certificates", "Select a certificate from the following list:", X509SelectionFlag.SingleSelection, ptr);
                        // Check if one has been returned

                        if (certificates != null && certificates.Count > 0)
                            certificate = certificates[0];

                    }
                }
            }
            finally
            {
                store.Close();
            }

            return certificate;


        }
    }

private void butCacLogin_Click(object sender, EventArgs e)
     {
         this.Hide();
         SmartCard sc = new SmartCard();
         sc.SmartCardLogon();
         this.Close();
     }