use-keys.md

The UseKeys Method

The UseKeys method is used to select documents based on a list of zero or more keys. In this way, it is similar to performing a multiple get using IBucket.Get<T>(IList<string> keys). The UseKeys method is also required when performing subqueries.

Note: You must import the Couchbase.Linq.Extensions namespace to use the UseKeys method.

Basic Usage

The call to UseKeys should be immediately after the call to Query<T>.

var context = new BucketContext(bucket);

var keys = new[] {"alesmith_brewing-wee_heavy", "ali_i_brewing-amber_ale"};

var query = from beer in context.Query<Beer>().UseKeys(keys)
            select beer;

The query in this example will return all Beer documents which match the list of keys.

The advantage of this approach over using ICouchbaseCollection.GetAsync<T> is that you may then expand upon the query by applying where predicates, sorting, select projections, joins to other documents, etc. However, for simple queries like the example above, using ICouchbaseCollection.GetAsync<T> will be more performant because it will work directly against the data nodes instead of passing through a query node.