gistfile1.cs

public static class StringExtensions
{
    public static string Hash(this string value, string salt)
    {
        return SHA1.Create().
                ComputeHash(Encoding.UTF8.GetBytes(salt + value)).
                Select(x => x.ToString("x2")).
                Aggregate((a, x) => a + x); 
    }
}

public static class IEnumerableExtensions
{
    public static void ForEach<T>(this IEnumerable<T> items, Action<T> action)
    {
        foreach (var item in items) action(item);
    }
}