using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        string address1 = "172 Drury Lane";

        string address2 = null;

        string city = "London";

        string postcode = "WC2B 5QR";

        var normalizedAddress = AddressNormalizer.Normalize(address1, address2, city, postcode);

        Console.WriteLine(normalizedAddress);

    }

}

​

public static class AddressNormalizer

{

    /// <summary>

    /// Performs some basic normalization of an address

    /// including lowercasing and removing non-alphanumeric 

    /// characters.

    /// </summary>

    public static string Normalize(params string[] addressParts)

    {

        if (addressParts == null) return string.Empty;

​

        var normalizedCharacters = addressParts

            .Where(s => s != null)

            .SelectMany(s => s.ToLowerInvariant())

            .Where(c => Char.IsLetterOrDigit(c));

​

        var result = string.Join(string.Empty, normalizedCharacters);

​

        return result;

    }

}