private void SetUpRetriever()
    {
        string retrieverIdentifier = mQueryParameters.Get("retrieverIdentifier");

        if (retrieverIdentifier == null)
        {
            throw new InvalidOperationException("retrieverIdentifier has to be set in the query string when using this user control");
        }

        mContactDemographicsDataRetriever = Service.Resolve <IContactDemographicsDataRetrieverFactory>().Get(retrieverIdentifier);

        try
        {
            mContacts = mContactDemographicsDataRetriever.GetContactObjectQuery(mQueryParameters);
        }
        catch (PermissionException e)
        {
            RedirectToAccessDenied(e.Message);
        }
    }