Session: Querying: How to Filter by Field Presence

• To filter documents by whether they contain a particular field, use the LINQ extension method WhereExists() accessible from the Document Query.

• If a document doesn't contain the specified field, it is excluded from the query results.

• In this page:

  • Syntax
  • Examples

Syntax

// Only documents that contain field 'FirstName' will be returned

List<Employee> results = session
  .Advanced
  .DocumentQuery<Employee>()
  .WhereExists("FirstName")
   // Or use lambda expression: .WhereExists(x => x.FirstName)
  .ToList();

Parameters	Type	Description
fieldName	string	The name of the field you want to filter by
propertySelector	Expression<Func<T,TValue>>	The path to the field you want to filter by

Examples

Filter by Field Name

• Sync
• Async
• RQL

List<Employee> results = session
  .Advanced
  .DocumentQuery<Employee>()
  .WhereExists("FirstName")
  .ToList();

List<Employee> results = await asyncSession
  .Advanced
  .AsyncDocumentQuery<Employee>()
  .WhereExists("FirstName")
  .ToListAsync();

from Employees 
where exists("FirstName")

Filter by the Path to a Field

This is done by passing the path as a lambda expression:

• Sync
• Async
• RQL

List<Employee> results = session
  .Advanced
  .DocumentQuery<Employee>()
  .WhereExists(x => x.Address.Location.Latitude)
  .ToList();

List<Employee> results = await asyncSession
  .Advanced
  .AsyncDocumentQuery<Employee>()
  .WhereExists(x => x.Address.Location.Latitude)
  .ToListAsync();

from Employees 
where exists(Address.Location.Latitude)

The path can also be passed as a string:

• Sync
• Async
• RQL

List<Employee> results = session
  .Advanced
  .DocumentQuery<Employee>()
  .WhereExists("Address.Location.Latitude")
  .ToList();

List<Employee> results = await asyncSession
  .Advanced
  .AsyncDocumentQuery<Employee>()
  .WhereExists("Address.Location.Latitude")
  .ToListAsync();

from Employees 
where exists("Address.Location.Latitude")