Modify an Object Schema - .NET SDK

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Add a Property

Delete a Property
Modify a Property Type or Rename a Property
Migration Functions

The following examples demonstrate how to add, delete, and modify properties in a schema. First, make the required schema change. Then, create a corresponding migration function to move data from the original schema to the updated schema.

Note

Modify Schema Properties of a Synced Realm

The following page demonstrates how to modify schema properties of a local realm. Learn how to modify schema properties of a synced realm.

Note

Versions Update on Realm Open

Assume that each schema change in this example occurs after an application has used each version for some amount of time. New schema version numbers only apply once you open the realm with an updated schema and explicitly specify the new version number, so in order to get to version 3, you would first need to open the app with versions 1 and 2.

A realm using schema version 1 has a Person object type:

public class Person : RealmObject
{
    [PrimaryKey]
    [MapTo("_id")]
    public ObjectId Id { get; set; }
    public string FirstName { get; set; }
    public int Age { get; set; }
}

Add a Property

The following example adds a LastName property to the original Person schema:

public class Person : RealmObject
{
    [PrimaryKey]
    [MapTo("_id")]
    public ObjectId Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public int Age { get; set; }
}

Delete a Property

The following example uses a combined FullName property instead of the separate FirstName and LastName property in the original Person schema:

public class Person : RealmObject
{
    [PrimaryKey]
    [MapTo("_id")]
    public ObjectId Id { get; set; }
    public string FullName { get; set; }
    public int Age { get; set; }
}

Modify a Property Type or Rename a Property

The following example modifies the Age property in the original Person schema by renaming it to Birthday and changing the type to DateTimeOffset:

public class Person : RealmObject
{
    [PrimaryKey]
    [MapTo("_id")]
    public ObjectId Id { get; set; }
    public string FullName { get; set; }
    public DateTimeOffset Birthday { get; set; }
}

Migration Functions

Tip

Bypass Migration During Development

When developing or debugging your application, you may prefer to delete the realm instead of migrating it. Use the ShouldDeleteIfMigrationNeeded flag to delete the database automatically when a schema mismatch would require a migration.

Never release an app to production with this flag set to true.

To migrate the realm to conform to the updated Person schema, the set the realm's schema version to 4 and define a migration function to set the value of FullName based on the existing FirstName and LastName properties and the value of Birthday based on Age:

1 var config = new RealmConfiguration
2 {
3     SchemaVersion = 4,
4     MigrationCallback = (migration, oldSchemaVersion) =>
5     {
6         var oldPeople = migration.OldRealm.All<Person>();
7         var newPeople = migration.NewRealm.All<Person>();
8 
9         // Migrate Person objects
10         for (var i = 0; i < newPeople.Count(); i++)
11         {
12             var oldPerson = oldPeople.ElementAt(i);
13             var newPerson = newPeople.ElementAt(i);
14 
15             // Changes from version 1 to 2 (adding LastName) will occur automatically when Realm detects the change
16 
17             // Migrate Person from version 2 to 3: replace FirstName and LastName with FullName
18             // LastName doesn't exist in version 1
19             if (oldSchemaVersion < 2)
20             {
21                 newPerson.FullName = oldPerson.FirstName;
22             }
23             else if (oldSchemaVersion < 3)
24             {
25                 newPerson.FullName = $"{oldPerson.FirstName} {oldPerson.LastName}";
26             }
27 
28             // Migrate Person from version 3 to 4: replace Age with Birthday
29             if (oldSchemaVersion < 4)
30             {
31                 var birthYear = DateTimeOffset.UtcNow.Year - oldPerson.Age;
32                 newPerson.Birthday = new DateTimeOffset(birthYear, 1, 1, 0, 0, 0, TimeSpan.Zero);
33             }
34         }
35     }
36 };
37 var realm = Realm.GetInstance(config);

Note

Unity does not support the dynamic keyword when using IL2CPP

Unity has various scripting restrictions and does not support the dynamic keyword when using IL2CPP. Instead you can cast the Dynamic value to the type you want to use. In the following example, the retrieved Person objects are explicitly converted to an IQueryable<RealmObject>.

var oldPeople = (IQueryable<RealmObject>)migration.OldRealm.DynamicApi.All("Person"); // store results of retrieved Person objects

Tip

1	var config = new RealmConfiguration
2	{
3	SchemaVersion = 4,
4	MigrationCallback = (migration, oldSchemaVersion) =>
5	{
6	var oldPeople = migration.OldRealm.All<Person>();
7	var newPeople = migration.NewRealm.All<Person>();
8
9	// Migrate Person objects
10	for (var i = 0; i < newPeople.Count(); i++)
11	{
12	var oldPerson = oldPeople.ElementAt(i);
13	var newPerson = newPeople.ElementAt(i);
14
15	// Changes from version 1 to 2 (adding LastName) will occur automatically when Realm detects the change
16
17	// Migrate Person from version 2 to 3: replace FirstName and LastName with FullName
18	// LastName doesn't exist in version 1
19	if (oldSchemaVersion < 2)
20	{
21	newPerson.FullName = oldPerson.FirstName;
22	}
23	else if (oldSchemaVersion < 3)
24	{
25	newPerson.FullName = $"{oldPerson.FirstName} {oldPerson.LastName}";
26	}
27
28	// Migrate Person from version 3 to 4: replace Age with Birthday
29	if (oldSchemaVersion < 4)
30	{
31	var birthYear = DateTimeOffset.UtcNow.Year - oldPerson.Age;
32	newPerson.Birthday = new DateTimeOffset(birthYear, 1, 1, 0, 0, 0, TimeSpan.Zero);
33	}
34	}
35	}
36	};
37	var realm = Realm.GetInstance(config);