Filter facets

Facets are used for grouping documents based on some criteria, for example specific terms or date range. 

A filter facet returns a count of all search results that match a filter. The filter can be an expression, as used with the Filter method, so can range from a single criterion to very complex criteria made up of multiple sub criteria.

To request a filter facet, use the FilterFacet method, which has two parameters: name and filter or filter expression. You retrieve the resulting facet from the search results object using a method with the same name but with only a name parameter. The returned object has a single property, Count, which is the number of documents that match the search query and filter.

The following example shows a sample search for all products which requests, and retrieves the value from, two filter facets.

var result = client.Search<Product>()
  .FilterFacet("In stock", x => x.InStock.Match(true))
  .FilterFacet("In stock on sale", 
    x => x.InStock.Match(true) & x.OnSale.Match(true))
  .GetResult()

int inStock = result.FilterFacet("In stock").Count;

int inStockAndOnSale = result
  .FilterFacet("In stock on sale").Count;