This class is given to you when you migrate your database from one version to another. It contains two properties: OldRealm and NewRealm. The NewRealm is the one you should make sure is up to date. It will contain models corresponding to the configuration you've supplied. You can read from the OldRealm and access properties that have been removed from the classes by using the dynamic API.
Migration Class Documentation
コード例 #1
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        internal override Realm CreateRealm(RealmSchema schema)
        {
            var srHandle = new SharedRealmHandle();

            var configuration = new Native.Configuration
            {
                Path = DatabasePath,
                read_only = IsReadOnly,
                delete_if_migration_needed = ShouldDeleteIfMigrationNeeded,
                schema_version = SchemaVersion
            };

            Migration migration = null;
            if (MigrationCallback != null)
            {
                migration = new Migration(this, schema);
                migration.PopulateConfiguration(ref configuration);
            }

            var srPtr = IntPtr.Zero;
            try
            {
                srPtr = srHandle.Open(configuration, schema, EncryptionKey);
            }
            catch (ManagedExceptionDuringMigrationException)
            {
                throw new AggregateException("Exception occurred in a Realm migration callback. See inner exception for more details.", migration?.MigrationException);
            }

            srHandle.SetHandle(srPtr);
            return new Realm(srHandle, this, schema);
        }