Simple class for creating hashes. Default uses MD5 encryption.

ICryptography.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Secure.Hash
{
    public interface ICryptography
    {
        string HashString(string original);
    }
}

StringHasher.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Web;

namespace Secure.Hash
{
    public class StringHasher : ICryptography
    {
        private readonly HashAlgorithm _algorithm;
        private readonly Encoding _encoder;

        public StringHasher()
            : this(MD5.Create()) { }

        public StringHasher(HashAlgorithm algorithm)
            : this(algorithm, new ASCIIEncoding()) { }

        public StringHasher(HashAlgorithm algorithm, Encoding encoder)
        {
            _algorithm = algorithm;
            _encoder = encoder;
        }

        #region ICryptography Members

        public string HashString(string original)
        {
            string hash;
            if (string.IsNullOrEmpty(original))
                hash = string.Empty;
            else
            {
                var bytes = _encoder.GetBytes(original);
                var result = _algorithm.ComputeHash(bytes);
                var sb = new StringBuilder();
                for (var i = 0; i < result.Length; i++)
                    sb.Append(result[i].ToString("X2"));

                hash = sb.ToString();
            }
            return hash;
        }

        #endregion
    }
}