new While
{
    Condition = true,
    Body = new Receive
    {
        ServiceContractName = Constants.POContractName,
        OperationName = Constants.UpdatePOName,                                    
        CorrelatesWith = poidHandle, // identifies that the UpdatePO operation is waiting on the PurchaseOrderId that was used to initialize this handle
        CorrelatesOn = new MessageQuerySet // the query that is used on an incoming message to find the requisite PurchaseOrderId specified in the correlation
        {
            // Id is the name of the incoming parameter within the PurchaseOrder
            { "PoId", new XPathMessageQuery("sm:body()/defns:PurchaseOrder/defns:Id", Constants.XPathMessageContext) } 
        },
        Content = ReceiveContent.Create(new OutArgument<PurchaseOrder>(po)) // creates a ReceiveMessageContent
    }
},