public static bool IsCertificatePresent(string issuerToFind, out string errorInfo)
        {
            errorInfo = String.Empty;
            try
            {
                X509Store store = new X509Store(StoreName.My,
                                                System.Security.Cryptography.X509Certificates.StoreLocation.CurrentUser);

                store.Open(OpenFlags.ReadOnly);
                //for example, issuerToFind = "CN=Your Certificate Authority CA";

                //X509Certificate2Collection collectionX509 =
                //        store.Certificates.Find(X509FindType.FindBySubjectName,
                //                subject, true);
                //bool found = collectionX509.Count > 0;

                //iterate in store Certificates and check if we have ours:
                bool found = false;
                X509Certificate2Collection collectionX509 =
                        (X509Certificate2Collection)store.Certificates;
                foreach (X509Certificate2 x509 in collectionX509)
                {
                    string issuer = x509.GetIssuerName();
                    if (issuer == issuerToFind)
                    { found = true; break; }

                }
                store.Close();
                return found;
            }
            catch (Exception ex_certificate_present)
            {
                errorInfo = ex_certificate_present.Message;
                return false;
            }

        }	
	

	[DllImport("coredll.dll")]
        private extern static int GetDeviceUniqueID(
            [In, Out] byte[] appdata,
            int cbApplictionData,
            int dwDeviceIDVersion,
            [In, Out] byte[] deviceIDOuput,
            out uint pcbDeviceIDOutput);

	public static string DeviceID(string ApplicationName)
        {
            byte[] buffer = GetDeviceID(ApplicationName);
            StringBuilder sb = new StringBuilder();
            for (int x = 0; x < buffer.Length; x++)
            {
                //sb.Append('{');
                sb.Append(string.Format("{0:x2}", buffer[x]));
                //sb.Append("} ");
            }

            return sb.ToString();

        }

        private static byte[] GetDeviceID(string AppString)
        {
            // Call the GetDeviceUniqueID
            byte[] AppData = new byte[AppString.Length];
            for (int count = 0; count < AppString.Length; count++)
                AppData[count] = (byte)AppString[count];
            int appDataSize = AppData.Length;
            byte[] DeviceOutput = new byte[20];
            uint SizeOut = 20;
            GetDeviceUniqueID(AppData, appDataSize, 1, DeviceOutput, out SizeOut);
            return DeviceOutput;
        }

	

	[DllImport("sms.dll")]
      	private static extern IntPtr SmsGetPhoneNumber(IntPtr psmsaAddress);

	    public enum AddressType 
	    {
		    /// 
Unknown phone number type.
		    Unknown,
		    /// 
International phone number.
		    International,
		    /// 
National phone number.
		    National,
		    /// 
Network-specific phone number.
		    NetworkSpecific,
		    /// 
Subscriber phone number.
		    Subscriber,
		    /// 
Alphanumeric phone number.
		    Alphanumeric,
		    /// 
Abbreviated phone number.
		    Abbreviated
	    }

	    public struct PhoneAddress
	    {
		    /// 
The address type.
		    public AddressType AddressType;
		    /// 
The phone number in string format.
		    public String Address;
	    }

        unsafe public static PhoneAddress SIMPhoneNumber()
        {
		    PhoneAddress phoneAddress = new PhoneAddress();

			Byte[] buffer = new Byte[516];
			fixed (byte* pAddr = buffer) 
			{
				IntPtr res = SmsGetPhoneNumber((IntPtr)pAddr);
				if (res != IntPtr.Zero)
					throw new Exception("Could not get phone number from SIM");

				byte *pCurrent = pAddr;
                phoneAddress.AddressType = (AddressType)Marshal.ReadInt32((IntPtr)pCurrent);
                pCurrent += Marshal.SizeOf(phoneAddress.AddressType);
                phoneAddress.Address = Marshal.PtrToStringUni((IntPtr)pCurrent);
			}

            return phoneAddress;

        }

	

	public string ApplicationFolder
        {
            get
            { return GetApplicationDirectory(); }
        }
        private string GetApplicationDirectory()
        {
            return Path.GetDirectoryName(
                            System.Reflection.Assembly.GetExecutingAssembly().GetName().CodeBase
                            ).Replace(@"file:\", "");
        }
	

	public bool LoadConfigSettings(out string errorInfo)
        {
            errorInfo = String.Empty;
            try
            {
                string appConfigFile = Path.Combine(GetApplicationDirectory(), ".config");
                if (!File.Exists(appConfigFile))
                { throw (new System.Exception("Config File\n" + appConfigFile + "\nnot found")); }

                DataSet appSettings = new DataSet("settings");
                appSettings.ReadXml(appConfigFile, XmlReadMode.Auto);

                if (appSettings.Tables.Count != 0)
                {
                    //load!
                    DataRow dr = appSettings.Tables[0].Rows[0];
                    //get Web service URL
                    m_WebServiceURL = dr["webserviceURL"].ToString();
                    //log error? 1/0:
                    m_LogError = (dr["logerror"].ToString() != String.Empty);

                    return true;
                }
                else
                { throw (new System.Exception("Invalid Config File\n" + appConfigFile )); }

            }
            catch ( Exception ex_load_config )
            {
                //throw (new System.Exception(ex_load_config.ToString()));
                errorInfo = ex_load_config.Message;
                return false;
                
            }
        }
	

	public void SaveToLog(string Message)
        {
            string LogFile = GetApplicationDirectory();
            LogFile = Path.Combine(LogFile, "log_" + System.DateTime.Now.ToString("MM_dd_yyyy") + ".txt");

            try
            {
                StreamWriter fileStream;
                if (File.Exists(LogFile))
                { fileStream = File.AppendText(LogFile); }
                else
                { fileStream = File.CreateText(LogFile); }

                Message = System.DateTime.Now.ToString("MM/dd/yyyy") + " " +
                            System.DateTime.Now.ToString("HH:mm:ss") + " - " +
                            Message;

                fileStream.WriteLine(Message);
                fileStream.Close();

            }

            catch (Exception ex_save_to_log)
            {
                //
                throw (new System.Exception("\n" + LogFile + "\n" + ex_save_to_log.ToString()));
            }
        }

	

	
	...
	string ParentPath = "\\Program Files";
	DirectoryInfo ParentFolder = new DirectoryInfo(ParentPath);

	//get files:
	FileInfo[] FileList = ParentFolder.GetFiles();
	//for sorting:
	FileInfoComparer FileInfoComparer = new FileInfoComparer();
	//sort
	Array.Sort(FileList, FileInfoComparer);
	...
	

	class FileInfoComparer : System.Collections.IComparer
    	{
        	int IComparer.Compare(Object objFileInfo1, Object objFileInfo2)
	        {
        	    System.IO.FileInfo FileInfo1 = (System.IO.FileInfo)objFileInfo1;
	            System.IO.FileInfo FileInfo2 = (System.IO.FileInfo)objFileInfo2;

	            return String.Compare(FileInfo1.Name, FileInfo2.Name);
        	}
	}