[ElasticType(Name = "WebResource", SearchAnalyzer = "full_name", IndexAnalyzer = "partial_name", DateDetection = true, NumericDetection = true)]
public class WebResource
{
    public string _id;
    [ElasticProperty(Type = FieldType.integer_type, Index = FieldIndexOption.not_analyzed)]
    public string Id
    {
        get
        {
            if (_id == null || _id == Guid.Empty.ToString())
            {
                _id = Guid.NewGuid().ToString();
            }
            return _id;
        }
        set
        {
            _id = value;
        }
    }

    [ElasticProperty(Type = FieldType.string_type, Index = FieldIndexOption.analyzed)]
    public string Keywords { get; set; }

    [ElasticProperty(Type = FieldType.string_type, Index = FieldIndexOption.analyzed)]
    public string Content { get; set; }
}

Client.Search<WebResource>(g => g.Query(k => k.Term(l => l.Content, searchText) || k.Term(l => l.Keywords, searchText)).Highlight(k => k.OnFields(p => p.OnField("Keywords"), p => p.OnField("Content")).FragmentSize(200)));

Action<HighlightFieldDescriptor<WebResource>> actWeb = (t) => t.OnField(g => g.Content);
Action<HighlightFieldDescriptor<WebResource>> actKey = (t) => t.OnField(g => g.Keywords);

Action<HighlightDescriptor<WebResource>> higDesc = t => t.OnFields(actWeb,actKey);

SearchDescriptor<WebResource> searchdesc = new SearchDescriptor<WebResource>();

searchdesc.Query( t => t.Term( k => k.Content,searchText) || t.Term( l =>l.Keywords,searchText));
searchdesc.Highlight(higDesc);

 var resp = Client.Search(searchdesc);