Bug System.DirectoryServices.DirectorySearcher

The field: internal SearchResultCollection? searchResult;

was never set. In older versions of the lib, the field was set in FindAll() method:

  SearchResultCollection resultCollection = new SearchResultCollection(root, hSearchResult, strArray, this);
  this.searchResult = resultCollection;
  return resultCollection;

Now:

        return new SearchResultCollection(clonedRoot, resultsHandle, properties, this);

As result impossible to retrieve DirsyncCookie.