Use filters to narrow down search results or for database-like queries. 

You can use the `Filter` method to filter Boolean and nullable _Boolean_ fields in a couple of ways, as shown in the following use cases and examples.

## Existence

To search for documents where a Boolean field has a value, use the `Exists` method. The following search finds blog posts that have an Approved property with a value. The below code is similar to the LINQ query `Where(x => x.Approved.HasValue)`.

You can negate the filter with an exclamation point (!); to instead find all blog posts that lack an `Approved` property, use the following code.

## Match true or false

For exact matching, use the `Match` method. The following search matches blog posts whose `Approved` property is true. The LINQ equivalent is `Where(x => x.Approved)`.