I am stuck on interfaces and inheritance. If I implement two classes who both have an interface each, how would I be able to add the properties of Class A and B together? For instance I wanted to associate `firstitem` with the `seconditem`.

```
public interface IAlpha
{
  [WebInvoke(Method = "POST", BodyStyle = WebMessageBodyStyle.Bare, RequestFormat = WebMessageFormat.Xml, ResponseFormat = WebMessageFormat.Xml, UriTemplate = "/AddBravoToAlpha/{firstitem}/{seconditem}")]
  void AddBravoToAlpha(int firstitem, int seconditem);
}
public interface IBravo
{
    // what goes in here?
}
public Class Alpha
{
    public Alpha()
    {
        AlphaAdd = new List<Bravo>();
    }
   int Firstitem { get; set }
   public List<Bravo> AlphaAdd { get; set; }
}
public Class Bravo 
{
   public Bravo() 
   {
        BravoAdd = new List<Alpha>(); //not sure if Bravo can access Alpha (derived class)
   }
   int Seconditem { get; set }
   Guid Indexer { get; set }
   public List<Alpha> BravoAdd { get; set; }
}
public Class BravoDoesAlpha : IBravo, IAlpha //????
{
    List<Alpha> alpha = new List<Alpha>();
    List<Bravo> bravo = new List<Bravo>();

    public void AddBravoToAlpha(int firstitem, int seconditem)
    {
        var result = alpha.Where(n => String.Equals(n.Firstitem, firstitem)).FirstOrDefault();
        var result1 = bravo.Where(n => String.Equals(n.Seconditem, seconditem)).FirstOrDefault();
        if (result != null)
        {
            result.BravoAdd.Add(new Alpha() { Firstitem = firstitem });
        }
        if (result1 != null)
        {
            result1.AlphaAdd.Add(new Bravo() { Seconditem = seconditem });
        }

    }
}

```