Hashed texts based on user's passwords

I have finished my first project using ASP.NET MVC. I did not have to wait long to realise I have essentially violated all possible codes of good programming. Well, experience comes with practice.

One of the styles I completely missed was Dependency Injection Principle. It was far too late I could re-write the project and apply it.

DI took me some time to understand. Based on this very simple project, I would like experience programmers to give me some reviews, whether I have sorted the DI correctly.

This is a very simple task. I want to generate hashed texts based on password provided by users. I know I could sort this in couple of lines but I wanted to do something I could apply DI.

I split the whole solution into two projects. The first project contains hashing algorithms, the second the main function to generate hashed text. I tried to lose all possible couplings based everything on interfaces.

So, GeneratePassword.computetHashedPassword() uses injected object of HashingAlgorithm to make GeneratePassword independent to it. On the other hand, HashingAlgorithm using one of the System interfaces, System.Security.Cryptography.HashAlgorithm. This way I tried to make hashing algorithm also independent.

class Program
{
    static void Main(string[] args)
    {
        IGeneratePassword gp;
        string password = "propiotr";

        Console.WriteLine("By bew class:");
        gp = new GeneratePassword(new XAlgorithm(new SHA256Cng()));
        Console.WriteLine(string.Format("{0,19}: {1}", "HashedPassword", gp.GetHashedPassword(password)));
        Console.WriteLine(string.Format("{0,19}: {1}", "Password", gp.Password));
        Console.WriteLine(string.Format("{0,19}: {1}", "Password Salt", gp.PasswordSalt));
        Console.WriteLine();
    }
}

Hashing Algorithms

public interface IHashAlgorithm
{
    string GetHashedText(string text);
}

public class XAlgorithm : IHashAlgorithm
{
    private System.Security.Cryptography.HashAlgorithm sysHashAlgorithm;

    public XAlgorithm(System.Security.Cryptography.HashAlgorithm hashAlgorithm)
    {
        this.sysHashAlgorithm = hashAlgorithm;
    }

    public string GetHashedText(string text)
    {
        string hashedtext = getHashX(text);
        for (int i = 0; i < 255; i++)
            hashedtext = getHashX(hashedtext);
        return hashedtext;
    }

    private string getHashX(string text)
    {
        byte[] bytes = Encoding.Unicode.GetBytes(text);
        byte[] hash = sysHashAlgorithm.ComputeHash(bytes);
        string hashString = string.Empty;
        foreach (byte x in hash)
        {
            hashString += String.Format("{0:x2}", x);
        }
        return hashString;
    }
}

public class MD5Algorithm : IHashAlgorithm
{
    public string GetHashedText(string text)
    {
        XAlgorithm ha = new XAlgorithm(new MD5Cng());
        return ha.GetHashedText(text);
    }
}

public class Sha256Algorithm : IHashAlgorithm
{
    public string GetHashedText(string text)
    {
        XAlgorithm ha = new XAlgorithm(new SHA256Cng());
        return ha.GetHashedText(text);
    }
}    

PasswordEncryption

public interface IGeneratePassword
{
    string Password { get; set; }
    string HashedPassword { get; }
    string PasswordSalt { get; }
    string GetHashedPassword(string password);
}

public class GeneratePassword : IGeneratePassword
{
    private IHashAlgorithm hashAlgorithm;
    private string password;
    private string passwordSalt;
    private string hashedPassword;

    public string Password
    {
        get { return password; }
        set { this.password = value; }
    }
    public string HashedPassword
    {
        get
        {
            computetHashedPassword();
            return hashedPassword;
        }
    }
    public string PasswordSalt
    {
        get { return passwordSalt; }
    }

    public GeneratePassword(IHashAlgorithm hashAlgorithm)
    {
        this.hashAlgorithm = hashAlgorithm;
        this.passwordSalt = getRandomString(25);
    }

    public string GetHashedPassword(string password)
    {
        this.password = password;
        return HashedPassword;
    }

    private void computetHashedPassword()
    {
        if (string.IsNullOrEmpty(this.password))
            throw new ArgumentNullException("Cannot compute a hashed password for the empty property 'Password'");
        this.hashedPassword = hashAlgorithm.GetHashedText(this.password + this.passwordSalt);
    }

    private static string getRandomString(int number)
    {
        string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
        Random random = new Random();
        return new string(Enumerable.Repeat(chars, number)
                                    .Select(s => s[random.Next(s.Length)])
                                    .ToArray());
    }
}