Filters
Describes how to use filters in Optimizely Search & Navigation.
Filters narrow down search results, limiting a free-text search for books to a specific category or for database-like queries.
Search requests consist primarily of queries and filters. Queries and filters are similar. Filters perform better but do not affect scoring (sorting by relevance).
The .NET client API supports most filter types supported by the REST API and a fluent API for common filtering operations.
Assume a BlogPost
class with a Title
string property. The following code finds BlogPosts
titled Find.
var searchQuery = client.Search<BlogPost>()
.Filter(x => x.Title.Match("Find"));
The Search<TSource>
method returns an instance of ITypeSearch<TSource>
, which acts as a builder class for a search request. Using the Filter
extension method, you can add a filter to the search request by supplying an expression that returns an instance of the Filter
class. The client API has several extension methods for value types and strings that return filters, such as the Match
method above.
Group filters
You can group filters using Boolean operators. For example, the following code finds blog posts titled Find or Search.
var searchQuery = client.Search<BlogPost>()
.Filter(x => x.Title.Match("Find")
| x.Title.Match("Search"));
Assuming the BlogPost
class has a Tag
property, the following code finds blog posts titled Search and tagged with Find, or titled Find (with no requirements for tags).
var searchQuery = client.Search<BlogPost>()
.Filter(x => (x.Title.Match("Search")
& x.Tags.Match("Find"))
| x.Title.Match("Find"));
Call Filter multiple times
You can call the filter
 method numerous times, which is useful at runtime if you determine the filters you want to apply, such as filters that depend on user input. For example, you can modify the first part of the filter expression above.
var searchQuery = client.Search<BlogPost>()
.Filter(x => x.Title.Match("Search"))
.Filter(x => x.Tags.Match("Find"));
OrFilter method
If you invoke the Filter
method multiple times, the latter invocations' filters are combined with previous invocations' filters using AND. To combine them using OR, use the following code.
var searchQuery = client.Search<BlogPost>()
.Filter(x => x.Title.Match("Search"))
.Filter(x => x.Tags.Match("Find"))
.OrFilter(x.Title.Match("Find"));
If the OrFilter
method is called before the Filter
method, it is the same as calling the Filter
method, because there is no existing filter to OR-group it.
Complex and dynamically created filters
Sometimes, the Filter
and OrFilter
methods are not enough. For example, you build complex search queries dynamically at runtime based on user input. While the methods can handle most scenarios at compile time, creating multiple grouped Orfilters
at runtime is tricky and results in complex code. To build filters without regard to other filters and apply them to a search query, using the IClient
extension method BuildFilter
.
The BuildFilter
method requires a generic type parameter to which you apply the filter. The method returns an object of type FilterBuilder
. The FilterBuilder
class has And and Or methods, which you use to add filter expressions like the Filter
and OrFilter
methods. The FilterBuilder
class is implicitly convertible to the Filter class so that you can pass instances of it as arguments to the Filter
 and OrFilter
 methods and in filter expressions.
For example, you manage a restaurant search that uses two variables: cuisines and countries of type IEnumerable<string>
. Each may be null, but if not, you want to add a filter so that search results return only restaurants matching those cuisines or countries. Use the BuildFilter
method to accomplish this.
var q = ...some search string
ITypeSearch<Restaurant> query = client.Search<Restaurant>().For(q);
if (cuisines != null) {
var cuisineFilter = client.BuildFilter<Restaurant>();
foreach(var cuisine in cuisines) {
cuisineFilter = cuisineFilter.Or(x => x.Cuisine.Match(cuisine));
}
query = query.Filter(cuisineFilter);
}
if (countries != null) {
var countryFilter = client.BuildFilter<Restaurant>();
foreach(var country in countries) {
countryFilter = countryFilter.Or(x => x.Country.Match(country));
}
query = query.Filter(countryFilter);
}
var results = query.GetResult();
Filter methods
When filtering with the Filter
method, you provide an expression that returns a filter. To do so, use extension methods for properties that return filters. The above examples used the Match
extension method, but several other methods exist.
- Filter methods for:
You can also create custom extension methods to enhance the filtering functionality.
Updated 4 months ago