Reading and Writing

This page is a brief overview of performing basic reading and writing operations with the driver. All the operations available in the API are async utilizing Tasks.

For more information about interacting with the server, refer to the reference guide.

The rest of this document assumes the following class and collection:

public class Person
{
    public ObjectId Id { get; set; }

    public string Name { get; set; }

    public int Age { get; set; }

    public string Profession { get; set; }
}

var collection = db.GetCollection<Person>("people");

Inserting a document

To insert a document, use the InsertOneAsync method.

var jane = new Person { Name = "Jane McJane", Age = 24, Profession = "Hacker" };

await collection.InsertOneAsync(jane);

After insertion, the Jane’s Id property will contain the automatically generated identifier. For more on Id generation, see the reference guide.

Finding a Document

To find all the people who are younger than 42, use the Find method such as follows:

var people = await collection.Find(x => x.Age < 42).ToListAsync();

The lambda expression gets translated into the BSON filter { Age: { $lt: 42 } }. Not everything is supported via expression trees, but most of the common operations are. See the reference guide for more information.

Updating

To update a document, there are 2 methods for doing so. First, you can update specific fields. For instance, I’d like to change Tom’s profession to “Musician”.

var result = await collection.UpdateOneAsync(
    x => x.Name == "Tom",
    Builders<Person>.Update.Set(x => x.Profession, "Musician"));

This will generate a filter of { Name: "Tom" } and an update specification of { $set: { Profession: "Musician" } }. Only one document will get updated even if there is more than one person named “Tom” because we used UpdateOneAsync instead of UpdateManyAsync. More information on updates is available in the reference guide.

Alternatively, if we want to replace a document completely, we can use the ReplaceOneAsync method. Assuming Tom’s Id value is 550c4aa98e59471bddf68eef:

var tom = await collection.Find(x => x.Id == ObjectId.Parse("550c4aa98e59471bddf68eef"))
    .SingleAsync();

tom.Name = "Thomas";
tom.Age = 43;
tom.Profession = "Hacker";

var result = await collection.ReplaceOneAsync(x => x.Id == tom.Id, tom);

Deleting

Finally, to delete Tom, you would use the DeleteOneAsync or DeleteManyAsync methods, such as in the following:

var result = await collection.DeleteOneAsync(x => x.Id == tom.Id);