How to Advance filter for category and author in Smartsearch in kentico

I have created basic search and uses the SearchHelper to get smart search results based on the search paramaters.

Now creating the Advance search based on Category , Author etc but did not find the way to filter the result based on these condition.

I am looking for a way to display the results using the dataset that

// Prepare parameters
SearchParameters parameters = new SearchParameters()
{
SearchFor = searchText,
SearchSort = SearchHelper.GetSort(srt),
Path = path,
ClassNames = DocumentTypes,
CurrentCulture = culture,
DefaultCulture = defaultCulture,
CombineWithDefaultCulture = CombineWithDefaultCulture,
CheckPermissions = CheckPermissions,
SearchInAttachments = SearchInAttachments,
User = (UserInfo)CMSContext.CurrentUser,
SearchIndexes = Indexes,
StartingPosition = startPosition,
DisplayResults = displayResults,
NumberOfProcessedResults = numberOfProceeded,
NumberOfResults = 0,
AttachmentWhere = AttachmentsWhere,
AttachmentOrderBy = AttachmentsOrderBy,
BlockFieldOnlySearch = BlockFieldOnlySearch,
};

// Search
DataSet results = SearchHelper.Search(parameters);

The easiest way is to use the method:

SearchHelper.CombineSearchCondition()

The first parameter is the searchText, with the search terms you probably already have.

The second parameter is searchConditions, which can be formatted as per

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Alternatively you could just append your search conditions to your search text manually, separating each term with a space.

Remember that to filter based on any field they need to be selected as searchable in the SiteManager->Development->DocumentTypes->DocumentType->Search Tab.