public class HandleConcurrencyExceptionAttribute : FilterAttribute, IExceptionFilter
    {
        private PropertyMatchingMode _propertyMatchingMode;
        /// <summary>
        /// This defines when the concurrencyexception happens, 
        /// </summary>
        public enum PropertyMatchingMode
        {
            /// <summary>
            /// Uses only the field names in the model to check against the entity. This option is best when you are using 
            /// View Models with limited fields as opposed to an entity that has many fields. The ViewModel (or model) field names will
            /// be used to check current posted values vs. db values on the entity itself.
            /// </summary>
            UseViewModelNamesToCheckEntity = 0,
            /// <summary>
            /// Use any non-matching value fields on the entity (except timestamp fields) to add errors to the ModelState.
            /// </summary>
            UseEntityFieldsOnly = 1,
            /// <summary>
            /// Tells the filter to not attempt to add field differences to the model state.
            /// This means the end user will not see the specifics of which fields caused issues
            /// </summary>
            DontDisplayFieldClashes = 2
        }


        public HandleConcurrencyExceptionAttribute()
        {
            _propertyMatchingMode = PropertyMatchingMode.UseViewModelNamesToCheckEntity;
        }

        public HandleConcurrencyExceptionAttribute(PropertyMatchingMode propertyMatchingMode)
        {
            _propertyMatchingMode = propertyMatchingMode;
        }


        /// <summary>
        /// The main method, called by the mvc runtime when an exception has occured.
        /// This must be added as a global filter, or as an attribute on a class or action method.
        /// </summary>
        /// <param name="filterContext"></param>
        public void OnException(ExceptionContext filterContext)
        {
            if (!filterContext.ExceptionHandled && filterContext.Exception is DbUpdateConcurrencyException)
            {
                //Get original and current entity values
                DbUpdateConcurrencyException ex = (DbUpdateConcurrencyException)filterContext.Exception;
                var entry = ex.Entries.Single();
                //problems with ef4.1/4.2 here because of context/model in different projects.
                //var databaseValues = entry.CurrentValues.Clone().ToObject();
                //var clientValues = entry.Entity;
                //So - if using EF 4.1/4.2 you may use this workaround
                var clientValues = entry.CurrentValues.Clone().ToObject();
                entry.Reload();
                var databaseValues = entry.CurrentValues.ToObject();

                List<string> propertyNames;

                filterContext.Controller.ViewData.ModelState.AddModelError(string.Empty, "The record you attempted to edit "
                        + "was modified by another user after you got the original value. The "
                        + "edit operation was canceled and the current values in the database "
                        + "have been displayed. If you still want to edit this record, click "
                        + "the Save button again to cause your changes to be the current saved values.");
                PropertyInfo[] entityFromDbProperties = databaseValues.GetType().GetProperties(BindingFlags.FlattenHierarchy | BindingFlags.Public | BindingFlags.Instance);

                if (_propertyMatchingMode == PropertyMatchingMode.UseViewModelNamesToCheckEntity)
                {
                    //We dont have access to the model here on an exception. Get the field names from modelstate:
                    propertyNames = filterContext.Controller.ViewData.ModelState.Keys.ToList();
                }
                else if (_propertyMatchingMode == PropertyMatchingMode.UseEntityFieldsOnly)
                {
                    propertyNames = databaseValues.GetType().GetProperties(BindingFlags.Public).Select(o => o.Name).ToList();
                }
                else
                {
                    filterContext.ExceptionHandled = true;
                    UpdateTimestampField(filterContext, entityFromDbProperties, databaseValues);
                    filterContext.Result = new ViewResult() { ViewData = filterContext.Controller.ViewData };
                    return;
                }



                UpdateTimestampField(filterContext, entityFromDbProperties, databaseValues);

                //Get all public properties of the entity that have names matching those in our modelstate.
                foreach (var propertyInfo in entityFromDbProperties)
                {

                    //If this value is not in the ModelState values, don't compare it as we don't want
                    //to attempt to emit model errors for fields that don't exist.

                    //Compare db value to the current value from the entity we posted.

                    if (propertyNames.Contains(propertyInfo.Name))
                    {
                        if (propertyInfo.GetValue(databaseValues, null) != propertyInfo.GetValue(clientValues, null))
                        {
                            var currentValue = propertyInfo.GetValue(databaseValues, null);
                            if (currentValue == null || string.IsNullOrEmpty(currentValue.ToString()))
                            {
                                currentValue = "Empty";
                            }

                            filterContext.Controller.ViewData.ModelState.AddModelError(propertyInfo.Name, "Current value: "
                                 + currentValue);
                        }
                    }

                    //TODO: hmm.... how can we only check values applicable to the model/modelstate rather than the entity we saved?
                    //The problem here is we may only have a few fields used in the viewmodel, but many in the entity
                    //so we could have a problem here with that.
                    //object o = propertyInfo.GetValue(myObject, null);
                }

                filterContext.ExceptionHandled = true;

                filterContext.Result = new ViewResult() { ViewData = filterContext.Controller.ViewData };
            }
        }

using System.Diagnostics;
using System.IO;
using iTextSharp.text;
using iTextSharp.text.pdf;
using System.Text;

namespace EncryptPublicKey
{
    class Program
    {
        static void Main(string[] args)
        {
            using (var pdfDoc = new Document(PageSize.A4))
            {
                var pdfWriter = PdfWriter.GetInstance(pdfDoc, new FileStream("Test.pdf", FileMode.Create));

                var readPassword = Encoding.UTF8.GetBytes("123");//it can be null.
                var editPassword = Encoding.UTF8.GetBytes("456");
                int permissions = PdfWriter.ALLOW_PRINTING | PdfWriter.ALLOW_COPY;
                pdfWriter.SetEncryption(readPassword, editPassword, permissions, PdfWriter.STRENGTH128BITS);

                pdfDoc.Open();

                pdfDoc.Add(new Phrase("tst 0"));
                pdfDoc.NewPage();
                pdfDoc.Add(new Phrase("tst 1"));
            }

            Process.Start("TestEnc.pdf");
        }
    }
}

using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.X509;

namespace EncryptPublicKey
{
    /// <summary>
    /// A Personal Information Exchange File Info
    /// </summary>
    public class PfxData
    {
        /// <summary>
        /// Represents an X509 certificate
        /// </summary>
        public X509Certificate[] X509PrivateKeys { set; get; }

        /// <summary>
        /// Certificate's public key
        /// </summary>
        public ICipherParameters PublicKey { set; get; }
    }
}

using System;
using System.IO;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Pkcs;
using Org.BouncyCastle.X509;

namespace EncryptPublicKey
{
    /// <summary>
    /// A Personal Information Exchange File Reader
    /// </summary>
    public class PfxReader
    {
        X509Certificate[] _chain;
        AsymmetricKeyParameter _asymmetricKeyParameter;
       
        /// <summary>
        /// Reads A Personal Information Exchange File.
        /// </summary>
        /// <param name="pfxPath">Certificate file's path</param>
        /// <param name="pfxPassword">Certificate file's password</param>
        public PfxData ReadCertificate(string pfxPath, string pfxPassword)
        {
            using (var stream = new FileStream(pfxPath, FileMode.Open, FileAccess.Read))
            {
                var pkcs12Store = new Pkcs12Store(stream, pfxPassword.ToCharArray());
                var alias = findThePublicKey(pkcs12Store);
                _asymmetricKeyParameter = pkcs12Store.GetKey(alias).Key;
                constructChain(pkcs12Store, alias);
                return new PfxData { X509PrivateKeys = _chain, PublicKey = _asymmetricKeyParameter };
            }
        }

        private void constructChain(Pkcs12Store pkcs12Store, string alias)
        {
            var certificateChains = pkcs12Store.GetCertificateChain(alias);
            _chain = new X509Certificate[certificateChains.Length];

            for (int k = 0; k < certificateChains.Length; ++k)
                _chain[k] = certificateChains[k].Certificate;
        }

        private static string findThePublicKey(Pkcs12Store pkcs12Store)
        {
            string alias = string.Empty;
            foreach (string entry in pkcs12Store.Aliases)
            {
                if (pkcs12Store.IsKeyEntry(entry) && pkcs12Store.GetKey(entry).Key.IsPrivate)
                {
                    alias = entry;
                    break;
                }
            }

            if (string.IsNullOrEmpty(alias))
                throw new NullReferenceException("Provided certificate is invalid.");

            return alias;
        }
    }
}

using System.Diagnostics;
using System.IO;
using iTextSharp.text;
using iTextSharp.text.pdf;

namespace EncryptPublicKey
{
    class Program
    {
        static void Main(string[] args)
        {
            using (var pdfDoc = new Document(PageSize.A4))
            {
                var pdfWriter = PdfWriter.GetInstance(pdfDoc, new FileStream("Test.pdf", FileMode.Create));

                var certs = new PfxReader().ReadCertificate(@"D:\path\cert.pfx", "123");
                pdfWriter.SetEncryption(
                          certs: certs.X509PrivateKeys,
                          permissions: new int[] { PdfWriter.ALLOW_PRINTING, PdfWriter.ALLOW_COPY },
                          encryptionType: PdfWriter.ENCRYPTION_AES_128);

                pdfDoc.Open();

                pdfDoc.Add(new Phrase("tst 0"));
                pdfDoc.NewPage();
                pdfDoc.Add(new Phrase("tst 1"));
            }

            Process.Start("Test.pdf");
        }
    }
}

using System.Diagnostics;
using System.IO;
using iTextSharp.text;
using iTextSharp.text.pdf;

namespace EncryptPublicKey
{
    class Program
    {
        static void Main(string[] args)
        {
            PdfReader reader = new PdfReader("TestDec.pdf");
            using (var stamper = new PdfStamper(reader, new FileStream("TestEnc.pdf", FileMode.Create)))
            {
                var certs = new PfxReader().ReadCertificate(@"D:\path\cert.pfx", "123");
                stamper.SetEncryption(
                         certs: certs.X509PrivateKeys,
                         permissions: new int[] { PdfWriter.ALLOW_PRINTING, PdfWriter.ALLOW_COPY },
                         encryptionType: PdfWriter.ENCRYPTION_AES_128);
                stamper.Close();
            }

            Process.Start("TestEnc.pdf");
        }
    }
}

public class Order { 
    public decimal Price() { 
        var primaryBasePrice = 10000; 
        var branchDiscountBasePrice = 9000; 
        var taxPercentage = 9; 
        // calculate price 
    } 
}

public class Order 
{ 
    public decimal Price() { 
        return new PriceCalculator(this).Compute(); 
    } 
} 
public class PriceCalculator 
{ 
    private Order orderInstance ;
    public PriceCalculator(Order order) 
    { 
        orderInstance = order;
    } 
    public decimal Compute() 
    { 
        var primaryBasePrice = 10000; 
        var branchDiscountBasePrice = 9000; 
        var taxPercentage = 9; 
        // calculate price 
    } 
}

var hexValue = "0x00010471000001BF001F";

            byte[] bigNumber = new byte[]
            { 
                0, 0, 0, 1, 0, 4, 7, 1, 0, 0, 0, 0, 0, 1, 
                byte.Parse("B", System.Globalization.NumberStyles.HexNumber), 
                byte.Parse("F", System.Globalization.NumberStyles.HexNumber), 
                0, 0, 1, 
                byte.Parse("F", System.Globalization.NumberStyles.HexNumber) 
            };

            Array.Reverse(bigNumber);
            var bigInt = new System.Numerics.BigInteger(bigNumber);

let add = (x,y) => x + y;

context.Products.Cacheable(x => x.First())
context.Products.Cacheable(x => x.Count())
...