I have looked at the documentation, but can't find anything definitive on how to sort descending by a field in Umbraco using Examine. (I can sort Ascending fine!). I'd like to sort by create Date, descending.... so this is what I have

  <IndexSet SetName="NewsAndPressCyIndexSet" IndexPath="~/App_Data/TEMP/ExamineIndexes/NewsAndPressCy/" IndexParentId="1052">
<IndexAttributeFields>
  <add Name="id" />
  <add Name="nodeName" />
  <add Name="createDate" EnableSorting="true" Type="DateTime" />
  <add Name="path" />
</IndexAttributeFields>
<IndexUserFields>
  <add Name="articleHeadline" />
  <add Name="articleContent" />
</IndexUserFields>
<IncludeNodeTypes>
  <add Name="NewsArticle" />
</IncludeNodeTypes>
<ExcludeNodeTypes>
</ExcludeNodeTypes>

And then in my c#

        string searchProviderCollection = Library.Languages.LanguageHelper.GetLanguageNameFromNodeId(Node.GetCurrent().Id) == "cy-GB" ? "NewsAndPressCySearcher" : "NewsAndPressEnSearcher";

        BaseSearchProvider searcher = Examine.ExamineManager.Instance.SearchProviderCollection[searchProviderCollection];
        ISearchCriteria searchCriteria = searcher.CreateSearchCriteria(Examine.SearchCriteria.BooleanOperation.Or);
        StringBuilder searchQueryString = new StringBuilder();

      ... build up search string etc etc etc

        ISearchCriteria searchQuery = searchCriteria.RawQuery(searchQueryString.ToString());//rderByDescending();//rderByDescending(new string[] { "createDate" });
        //searchQuery.OrderByDescending();

        ISearchResults searchResults = searcher.Search(searchQuery);//rderByDescending(x => x.Fields.["createDate"]);//

Where do I specify that I would like to search Descending?