using System;

public class Program

{

    public static void Main()

    {

        var a = new Address();

        a.Street1 = null; 

        a.Unit = null;

        Console.Write(a.Street == String.Empty);

    }

}

​

public class Address

{

    public string Street1 {get; set;}

    public string Unit {get; set;}

​

    public string Street

    { 

        get  {  return String.Format("{0}{1}", this.Street1, !Null.IsNull(this.Unit) ? String.Format(" {0}", this.Unit) : string.Empty); }

    }

​

}

​

public static class Null

{

    public static bool IsNull(object value)

    {

        if (value == null)

        {

            return true;

        }

        return false;

    }

}

​