COM Interop with Client and Server

Question

Hello, I have a DLL to encrypt data. I need to use the Component Object Model(COM) Interop to be able to communicate two applications and both traffic the encrypted data through this DLL. Searching, I found examples of integrating with Microsoft Office, but not with another application.

As requested, follow the example I found on the Microsoft website( e em cursos do Devmedia)

using System.Collections.Generic;
using Excel = Microsoft.Office.Interop.Excel;
using Word = Microsoft.Office.Interop.Word;

class Account
{
public int ID { get; set; }
public double Balance { get; set; }
}


var bankAccounts = new List<Account> 
{
new Account 
{
    ID = 345,
    Balance = 541.27
},
new Account 
{
    ID = 123,
    Balance = -127.44
}
};


void DisplayInExcel(IEnumerable<Account> accounts,
       Action<Account, Excel.Range> DisplayFunc)
{
var excelApp = this.Application;
// Add a new Excel workbook.
excelApp.Workbooks.Add();
excelApp.Visible = true;
excelApp.Range["A1"].Value = "ID";
excelApp.Range["B1"].Value = "Balance";
excelApp.Range["A2"].Select();

foreach (var ac in accounts)
{
    DisplayFunc(ac, excelApp.ActiveCell);
    excelApp.ActiveCell.Offset[1, 0].Select();
}
// Copy the results to the Clipboard.
excelApp.Range["A1:B3"].Copy();

excelApp.Columns[1].AutoFit();
excelApp.Columns[2].AutoFit();
}

I was able to develop this code, based on research. But I don’t know if it fits this concept. Could you help me with this?

Classe DLL
using System;
using System.Security.Cryptography;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;

namespace PortalRH.DLL
{
[ComVisible(true), ClassInterface(ClassInterfaceType.None),
Guid("00AC4F7E-71B0-4BC7-AD8E-1175CD88457A")]
public class Criptografia : ICriptografia
{
    private string chave = "Exemplo";
    private string texto;
    public Criptografia(){}

    private static readonly byte[] initVectorBytes =    Encoding.ASCII.GetBytes("tu89geji340t89u2");

    // Esta constante é utilizado para determinar o tamanho da chave do algoritmo de encriptação.
    private const int keysize = 256;

    public static string Encrypt(string plainText, string passPhrase)
    {
        byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);
        using (PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null))
        {
            byte[] keyBytes = password.GetBytes(keysize / 8);
            using (RijndaelManaged symmetricKey = new RijndaelManaged())
            {
                symmetricKey.Mode = CipherMode.CBC;
                using (ICryptoTransform encryptor = symmetricKey.CreateEncryptor(keyBytes, initVectorBytes))
                {
                    using (MemoryStream memoryStream = new MemoryStream())
                    {
                        using (CryptoStream cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
                        {
                            cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
                            cryptoStream.FlushFinalBlock();
                            byte[] cipherTextBytes = memoryStream.ToArray();
                            return Convert.ToBase64String(cipherTextBytes);
                        }
                    }
                }
            }
        }
    }

    public static string Decrypt(string cipherText, string passPhrase)
    {
        byte[] cipherTextBytes = Convert.FromBase64String(cipherText);
        using (PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null))
        {
            byte[] keyBytes = password.GetBytes(keysize / 8);
            using (RijndaelManaged symmetricKey = new RijndaelManaged())
            {
                symmetricKey.Mode = CipherMode.CBC;
                using (ICryptoTransform decryptor = symmetricKey.CreateDecryptor(keyBytes, initVectorBytes))
                {
                    using (MemoryStream memoryStream = new MemoryStream(cipherTextBytes))
                    {
                        using (CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
                        {
                            byte[] plainTextBytes = new byte[cipherTextBytes.Length];
                            int decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);
                            return Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);
                        }
                    }
                }
            }
        }
    }


    public string Matricula()
    {
        const string matricula = "5444";
        string plaintext = Encrypt(matricula, chave);
        return (plaintext);
    }

    public string Contrato()
    {
        const string contrato = "67334";
        string plaintext = Encrypt(contrato, chave);
        return (plaintext);
    }
}
}

My interface

using System.Runtime.InteropServices;
namespace PortalRH.DLL
{
[InterfaceType(ComInterfaceType.InterfaceIsDual),
 Guid("37DFD392-8BC3-4A08-B69A-5FDF1B6DF4B1")]
public interface ICriptografia
{

    string Matricula();
    string Contrato();
}
}

Answer 1

Apparently your code is correct, I will share my experience, C# Interop with VB6/C# (VS 2012) may help you in some details that are missing.

1. Open the properties(properties) menu of your project (DLL) and follow the steps below to set up your DLL.
   
   
2. Excerpt DLL source code Interop:

[ClassInterface(ClassInterfaceType.None)]
[ProgId("Interop.MeuInteopId")]
public class MinhaClass: IMinhaClass
{
    public string Usuario { get; set; }
    public void Adicionar(MeuObj obj)
    {
         minhalista.Add(obj);            
    }
}

public string Pesquisar()
{
    return "teste";
}

3. Code snippet Interface

public interface IFarmPop
{
    void Adicionar(MeuObj obj)
    string Usuario { set; get; }

Obs: In my case only the methods that are in the interfaces are exposed in Interop, that is, when using the DLL in other applications, they will only have access to the methods that are in the Interface.**

"Exposing" your DLL to the world!

Within the development environment just reference your DLL, if everything goes well the exposed methods will be accessible. I do not know what language the other applications referred to in the question are in, but the process is similar.

For other applications to have access to your DLL (outside the development environment), it is necessary to register it with the tool Regasm.

According to Microsoft: Regasm is a tool that allows COM clients create classes. NET Framework transparently. Once a class is registered, any COM customer can use it as if the class was a class WITH.

You can also use installers to register your DLL, but if you want to register via command line follow the steps:

1. At command prompt navigate to: C: Windows Microsoft.NET Framework\"version of framwork" (version you compiled your DLL)
2. Execute the command: regasm.exe SuaDLL.dll /register /codebase /tlb