Quick Start - .NET SDK

Install Realm

Follow these steps to add the Realm .NET SDK to your project.

Import Realm

Add the following line to the top of your source files to use Realm:

using Realms;

Define Your Object Model

Your application's object model defines the data that you can store within Realm and synchronize to and from App Services.

The following code shows how to define an object model for an Item object. In this example, we have marked the Id field as the Primary Key and marked the Status property as optional. We've also chosen to use the MapTo attribute; properties will be stored in lower case on the server, but can use .NET-friendly casing on our property names when using Device Sync.

public partial class Item : IRealmObject
{
    [PrimaryKey]
    [MapTo("_id")]
    public ObjectId Id { get; set; } = ObjectId.GenerateNewId();
    [MapTo("assignee")]
    public string Assignee { get; set; }
    [MapTo("name")]
    public string? Name { get; set; }
    [MapTo("status")]
    public string? Status { get; set; }
}

Open a Local Realm

In a local-only realm, you open a realm with either the Realm.GetInstance() or Realm.GetInstanceAsync() method. Which method you use depends entirely on if and how you are using asynchronous patterns in your app. The following code shows how to use GetInstance():

var realm = Realm.GetInstance();

For more information, see: Open a Realm.

Create, Read, Update, and Delete Objects

When creating or updating documents, all writes must happen in a transaction.

The following code shows two methods for creating a new Realm object. In the first example, we create the object first, and then add it to the realm within a WriteAsync() method. In the second example, we create the document within the WriteAsync block, which returns a realm object we can further work with.

var testItem = new Item
{
    Name = "Do this thing",
    Status = ItemStatus.Open.ToString(),
    Assignee = "Aimee"
};
await realm.WriteAsync(() =>
{
    realm.Add(testItem);
});
// Or 
var testItem2 =
    await realm.WriteAsync(() =>
    {
        return realm.Add<Item>(new Item
        {
            Name = "Do this thing, too",
            Status = ItemStatus.InProgress.ToString(),
            Assignee = "Satya"
        });
    }
);

Upserting a document is the same as creating a new one, except you set the optional update parameter to true. In this example, we create a new Item object with a unique Id. We then insert an item with the same id but a different Name value. Because we have set the update parameter to true, the existing record is updated with the new name.

var id = ObjectId.GenerateNewId();
var item1 = new Item
{
    Id = id,
    Name = "Defibrillate the Master Oscillator",
    Assignee = "Aimee"
};
// Add a new person to the realm. Since nobody with the existing Id
// has been added yet, this person is added.
await realm.WriteAsync(() =>
{
    realm.Add(item1, update: true);
});
var item2 = new Item
{
    Id = id,
    Name = "Fluxify the Turbo Encabulator",
    Assignee = "Aimee"
};
// Based on the unique Id field, we have an existing person,
// but with a different name. When `update` is true, you overwrite
// the original entry.
await realm.WriteAsync(() =>
{
    realm.Add(item2, update: true);
});
// item1 now has a Name of "Fluxify the Turbo Encabulator"
// and item2 was not added as a new Item in the collection.

You also delete items within a WriteAsync() method. The following code shows how to delete a single Item from the collection and how to delete an entire collection:

realm.Write(() =>
{
    realm.Remove(myItem);
});
realm.Write(() =>
{
    realm.RemoveAll<Item>();
});

The following pages cover each of these topics in more detail:

• Create

• Update

• Delete

Finding, Filtering, and Sorting Documents

You search for documents with the Realm query engine, using either LINQ or the Realm Query Language (RQL). The following example finds all objects of type "Item":

var allItems = realm.All<Item>();

You filter results using either LINQ or RQL. This example uses LINQ to find all Items that have a status of "Open":

var openItems = realm.All<Item>()
    .Where(i => i.Status == "Open");

You can also sort results using LINQ or RQL:

var sortedItems = realm.All<Item>()
    .OrderBy(i => i.Status);

For details on querying, filtering, and sorting documents, see Filter and Sort Data - .NET SDK.

Watch for Changes

As document collections change, it is often important to make updates to the data on a client app. You can watch a realm, collection, or object for changes with the SubscribeForNotifications() method.

The following example shows how to add a notification handler on an entire realm collection:

// Observe realm notifications.
realm.RealmChanged += (sender, eventArgs) =>
{
    // The "sender" object is the realm that has changed.
    // "eventArgs" is reserved for future use.
    // ... update UI ...
};

You can also add notification handlers on collections and individual objects. For more information, refer to React to Changes.

Add Device Sync (Optional)

If you want to sync Realm data across devices, you can configure Atlas App Services and enable Device Sync. Once you do that, you then add sync to your client code.

app = App.Create(myRealmAppId);

var user = await app.LogInAsync(Credentials.Anonymous());

await user.LogOutAsync();

var config = new FlexibleSyncConfiguration(app.CurrentUser)
{
    PopulateInitialSubscriptions = (realm) =>
    {
        var myItems = realm.All<Item>().Where(n => n.OwnerId == myUserId);
        realm.Subscriptions.Add(myItems);
    }
};
// The process will complete when all the user's items have been downloaded.
var realm = await Realm.GetInstanceAsync(config);