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Session: Querying: How to Filter by Field Presence
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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.
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In this page:
Syntax
IDocumentQuery<T> WhereExists(string fieldName);
IDocumentQuery<T> WhereExists<TValue>(Expression<Func<T, TValue>> propertySelector);| 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
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:
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:
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")
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