I have the same classes on my server and on my web service. I have the following WebMethod:

[WebMethod]
        public int CreateOrder(List<Purchase> p, string username)
        {
            o.Add(new Order(p,username));

            return o.Count;
        }

However the following code, run at server:

protected void CartRepeater_ItemCommand(object source, RepeaterCommandEventArgs e)
    {
        List<Purchase> l = ((List<Purchase>)Session["Cart"]);

        if (e.CommandName == "Order")
        {
            localhost.ValidateService WS = new localhost.ValidateService();
            WS.CreateOrder(l, Session["username"].ToString());
        }
    }

gives the following error: Argument '1': cannot convert from 'System.Collections.Generic.List<Purchase>' to 'localhost.Purchase[]'.

How can I transfer the list<Purchase> object to the web service?

Thank you very much.