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Session: Querying: How to query?

Database can be queried using LINQ-enabled Query method with few custom extension that will be described later.

Syntax​

IRavenQueryable<T> Query<T>(string indexName = null, string collectionName = null,
                          bool isMapReduce = false);

IRavenQueryable<T> Query<T, TIndexCreator>()
  where TIndexCreator : AbstractIndexCreationTask, new();
Parameters
indexNamestringName of an index to perform query on
isMapReduceboolIndicates if queried index is a map/reduce index (modifies how we treat identifier properties).
Return Value
IRavenQueryableInstance implementing IRavenQueryable interface containing additional query methods and extensions.

The default value of a page size for a query is 128 results. In order to retrieve a different number of results in a single query use .Take(pageSize) method.

Example I - Basic​

// This is a Full Collection Query
// No auto-index is created since no filtering is applied

List<Employee> allEmployees = session
  .Query<Employee>() // Query for all documents from 'Employees' collection
  .ToList();         // Execute the query

// All 'Employee' entities are loaded and will be tracked by the session

Notice that by specifying Employee as a type parameter, we are not only defining a result type, but also marking name of collection that will be queried.

Example II - Syntax​

Queries can be performed using both LINQ syntaxes.

// This is a Full Collection Query
// No auto-index is created since no filtering is applied

List<Employee> allEmployees = await asyncSession
  .Query<Employee>() // Query for all documents from 'Employees' collection
  .ToListAsync();    // Execute the query

// All 'Employee' entities are loaded and will be tracked by the session 
// This is a Full Collection Query
// No auto-index is created since no filtering is applied

// Query for all documents from 'Employees' collection
IRavenQueryable<Employee> query = from employee in session.Query<Employee>()
                                select employee;
// Execute the query
List<Employee> allEmployees = query.ToList();

// All 'Employee' entities are loaded and will be tracked by the session

Example III - Querying specified index​

// This is a Full Collection Query
// No auto-index is created since no filtering is applied

// Query for all documents from 'Employees' collection
IRavenQueryable<Employee> query = from employee in asyncSession.Query<Employee>()
                                select employee;
// Execute the query
List<Employee> allEmployees = await query.ToListAsync();

// All 'Employee' entities are loaded and will be tracked by the session

or

// load all entities from 'Employees' collection
// where FirstName equals 'Robert'
// using 'Employees/ByName' index
List<Employee> query = (from employee in session.Query<Employee, Employees_ByName>()
                      where employee.FirstName == "Robert"
                      select employee).ToList();

Custom methods and extensions​

Available custom methods and extensions: