Read documents

Find a document

To search for a document in MongoDB you use the Find method on a IMongoCollection<T> reference. Find method accepts a FilterDefinition<T> parameter where T is the collection's type.

Syntax

IMongoCollection<T>.Find(FilterDefinition<T> filter)

Filters can be created using the Builders<T>.Filter definition builder which contain multiple filters. The following example finds a user document based on its Id. It does this using the equality filter Eq<T> on the id field.

C#

ReadDocuments.cs

// Get the collection
var personsCollection = usersDatabase.GetCollection<User>("users");

// Create an Equality Filter Definition
var personFilter = Builders<User>.Filter
    .Eq(person => person.Id, appPerson.Id);

// Find the document in the collection    
var personFindResult = await personsCollection
    .Find(personFilter).FirstOrDefaultAsync();

Bson

// Get the collection
var bsonPersonCollection = usersDatabase.GetCollection<BsonDocument>("users");

// Create a bson filter
var bsonPersonFilter = Builders<BsonDocument>.Filter.Eq("_id", appPerson.Id);

// Find a person using a class filter
var bsonPersonFindResult = await bsonPersonCollection
    .Find(bsonPersonFilter).FirstOrDefaultAsync();

// alternative for passing a filter argument
bsonPersonFindResult = await bsonPersonCollection
.Find(new BsonDocument("_id", appPerson.Id)).FirstOrDefaultAsync();

Shell

// You need to know the Id's value and type

db.users.findOne(
{
    "_id": ObjectId("5e5d11fe152a428290f30245")
})

Document

{
	"_id" : ObjectId("5e5d11fe152a428290f30245"),
	"gender" : 1,
	"firstName" : "Joan",
	"lastName" : "Kovacek",
	"userName" : "Joan68",
	"avatar" : "https://s3.amazonaws.com/uifaces/faces/twitter/kohette/128.jpg",
	"email" : "[e-mail]",
	"dateOfBirth" : ISODate("1961-02-04T21:38:05.235+02:00"),
	"address" : {
		"street" : "6266 Naomie Key",
		"suite" : "Suite 865",
		"city" : "East Brianton",
		"state" : "New York",
		"zipCode" : "72433",
		"geo" : {
			"lat" : 41.3698,
			"lng" : -57.0814
		}
	},
	"phone" : "123-456-789",
	"website" : "heidi.net",
	"company" : {
		"name" : "Hansen - Stiedemann",
		"catchPhrase" : "Versatile uniform orchestration",
		"bs" : "expedite proactive markets"
	},
	"salary" : 4000,
	"monthlyExpenses" : 3132,
	"favoriteSports" : [
		"Table Tennis",
		"Handball",
		"Water Polo",
		"Tennis",
		"Baseball",
		"Cricket",
		"Cycling"
	],
	"profession" : "Lawyer"
}

Notice that when filter used with BsonDocument, _id field name used instead of Id which is the property name on the User class. When you use Builders<User>.Filter this is done automatically for you by the driver, based on the Id serialization settings

Find multiple documents

To search for multiple documents follow the same process but this time use the ToList method. The following example finds all documents with female gender.

C#

ReadDocuments.cs

// Get the collection
var personsCollection = usersDatabase.GetCollection<User>("users");

// Create an equality filter on a user's gender
var femaleGenderFilter = Builders<User>.Filter
    .Eq(person => person.Gender, Gender.Female);
    
// Find all documents having female gender
var females = await personsCollection
    .Find(femaleGenderFilter).ToListAsync();

Bson

// Get the collection
var bsonPersonCollection = usersDatabase.GetCollection<BsonDocument>("users");

// Create an equality filter on gender
var bsonFemaleGenderFilter = Builders<BsonDocument>
            .Filter.Eq("gender", Gender.Female);

// Get all female users
var bsonFemales = await bsonPersonCollection
            .Find(bsonFemaleGenderFilter).ToListAsync();

Shell

db.users.find(
{
   "gender": 1
})

----------------

// sample document
{
	"_id" : ObjectId("5e8a35e2cc20587f34f0cc2a"),
	"gender" : 1,
	"firstName" : "Ruth",
	"lastName" : "Bruen",
	"userName" : "Ruth51",
	"avatar" : "https://s3.amazonaws.com/uifaces/faces/twitter/polarity/128.jpg",
	"email" : "[e-mail]",
	"dateOfBirth" : ISODate("1955-06-24T20:34:26.809+02:00"),
	"address" : {
		"street" : "9217 O'Kon Alley",
		"suite" : "Apt. 111",
		"city" : "Lake Nicklaus",
		"state" : "Indiana",
		"zipCode" : "12931",
		"geo" : {
			"lat" : 60.0623,
			"lng" : 175.3924
		}
	},
	"phone" : "[phone] x931",
	"website" : "linda.net",
	"company" : {
		"name" : "Cummerata, Kilback and Bashirian",
		"catchPhrase" : "Seamless user-facing success",
		"bs" : "orchestrate transparent infrastructures"
	},
	"salary" : 4000,
	"monthlyExpenses" : 3633,
	"favoriteSports" : [
		"Moto GP",
		"American Football",
		"Snooker",
		"Motor Sport",
		"Baseball"
	],
	"profession" : "Marketing Manager"
},
{
	"_id" : ObjectId("5e8a35e2cc20587f34f0cc2c"),
	"gender" : 1,
	"firstName" : "Sue",
	"lastName" : "Muller",
	"userName" : "Sue0",
	"avatar" : "https://s3.amazonaws.com/uifaces/faces/twitter/vm_f/128.jpg",
	"email" : "[e-mail]",
	"dateOfBirth" : ISODate("1965-11-08T19:19:54.681+02:00"),
	"address" : {
		"street" : "090 Diego Vista",
		"suite" : "Suite 562",
		"city" : "South Rexton",
		"state" : "Kentucky",
		"zipCode" : "62445",
		"geo" : {
			"lat" : -19.2521,
			"lng" : -129.7291
		}
	},
	"phone" : "1-887-789-2466",
	"website" : "lorenzo.name",
	"company" : {
		"name" : "Parker - Wilderman",
		"catchPhrase" : "Function-based executive pricing structure",
		"bs" : "iterate cutting-edge technologies"
	},
	"salary" : 4000,
	"monthlyExpenses" : 1601,
	"favoriteSports" : [
		"Basketball",
		"Table Tennis",
		"Cricket",
		"MMA",
		"Moto GP",
		"Golf",
		"Ice Hockey",
		"Beach Volleyball"
	],
	"profession" : "Pilot"
}