create a filter not a group filter - orchardcms

Question

I am creating a custom module in Orchard , I would like to create a query programmatically.
string queryName= "Product";
var item = _orchardServices.ContentManager.New("Query");
item.As<TitlePart>().Title =queryName;
_orchardServices.ContentManager.Create(item, VersionOptions.Draft);
if (!item.Has<IPublishingControlAspect>() && !item.TypeDefinition.Settings.GetModel<ContentTypeSettings>().Draftable)
_orchardServices.ContentManager.Publish(item);
var queryPart = item.As<QueryPart>();
queryPart.ContentItem.ContentType = queryName;
string desc =" filter for the query";
string contentType = "CommonPart.ChannelID.";
var filterGroupRecord = new FilterGroupRecord();
var filterRecord = new FilterRecord()
{
Category = "CommonPartContentFields",
Type = contentType,
Position = 0,
};
filterRecord.State = "<Form><Description>" + desc + "</Description><Operator>Equals</Operator><Value>ChannelId</Value></Form>";
filterGroupRecord.Filters.Add(filterRecord);
queryPart.FilterGroups.Insert(0, filterGroupRecord);
the problem is that：I want set a filters of the query,not a filters group.
could you tell me how to improve my code?

Answer 1

Database structure and class declarations make it impossible. Why do you need it?
Update:
I means that you must use FilterGroupRecord at least one.
But when Query published that Filter Group will be created automatically if query have not yet Filter Group (see at QueryPartHandler). You should add your filters to this group. And not needed to create new group.
var existingFilterGroup = queryPart.FilterGroups[0];
existingFilterGroup.Filters.Add(filterRecord);
Update 2:
To avoid problems with draftable query (and several other potential problems Orchard CMS: Adding default data to fields and then querying them) it is better to move the calling Publish method to the end of your code and other part of your code should be left unchanged. And in your case would be better if you will always publish your query without checking IPublishingControlAspect and Draftable.