Class Realm

A Realm instance (also referred to as a Realm) represents a Realm database.
Warning: Non-frozen Realm instances are not thread safe and can not be shared across threads. You must call GetInstance(RealmConfigurationBase?) on each thread in which you want to interact with the Realm.

Inheritance

object

Realm

Implements

IDisposable

Namespace: Realms

Assembly: Realm.dll

Syntax

public class Realm : IDisposable

Properties

Config

Gets the RealmConfigurationBase that controls this realm's path and other settings.

Declaration

public RealmConfigurationBase Config { get; }

Property Value

Type	Description
RealmConfigurationBase	The Realm's configuration.

DynamicApi

Gets an object encompassing the dynamic API for this Realm instance.

Declaration

[Preserve]
public Realm.Dynamic DynamicApi { get; }

Property Value

Type	Description
Realm.Dynamic	A Realm.Dynamic instance that wraps this Realm.

IsClosed

Gets a value indicating whether the instance has been closed via Dispose(). If true, you should not call methods on that instance.

Declaration

public bool IsClosed { get; }

Property Value

Type	Description
bool	true if closed, false otherwise.

IsFrozen

Gets a value indicating whether this Realm is frozen. Frozen Realms are immutable and will not update when writes are made to the database. Unlike live Realms, frozen Realms can be used across threads.

Declaration

public bool IsFrozen { get; }

Property Value

Type	Description
bool	true if the Realm is frozen and immutable; false otherwise.

IsInTransaction

Gets a value indicating whether there is an active write transaction associated with this Realm.

Declaration

public bool IsInTransaction { get; }

Property Value

Type	Description
bool	true if the Realm is in transaction; false otherwise.

See Also

BeginWrite()

Transaction

Schema

Gets the RealmSchema instance that describes all the types that can be stored in this Realm.

Declaration

public RealmSchema Schema { get; }

Property Value

Type	Description
RealmSchema	The Schema of the Realm.

UseLegacyGuidRepresentation

Gets or sets a value indicating whether to use the legacy representation when storing Guid values in the database.

Declaration

[Obsolete("It is strongly advised to migrate to the new Guid representation as soon as possible to avoid data inconsistency.")]
public static bool UseLegacyGuidRepresentation { get; set; }

Property Value

Type	Description
bool

Remarks

In versions prior to 10.10.0, the .NET SDK had a bug where it would store Guid values with architecture-specific byte ordering (little-endian for most modern CPUs) while the database query engine and Sync would always treat them as big-endian. This manifests as different string representations between the SDK and the database - e.g. "f2952191-a847-41c3-8362-497f92cb7d24" instead of "912195f2-47a8-c341-8362-497f92cb7d24" (notice the swapped bytes in the first 3 components). Starting with 10.10.0, big-endian representation is the default one and a seamless one-time migration is provided for local (non-sync) Realms. The first time a Realm is opened, all properties holding a Guid value will be updated from little-endian to big-endian format and the .NET SDK will treat them as such. There should be no noticeable change when reading/writing data from the SDK, but you should see consistent values when accessing the Realm file from Realm Studio or other SDKs.
For synchronized Realms, such a migration is impossible due to the distributed nature of the data. Therefore, the assumption is that the Guid representation in Atlas if authoritative and the SDK values should be updated to match it. THIS MEANS THAT THE SDK WILL START REPORTING A DIFFERENT STRING REPRESENTATION OF EXISTING GUID DATA COMPARED TO pre-10.10.0. If you are querying 3rd party systems from the SDK, you might see unexpected results. To preserve the existing behavior (little-endian in the SDK, big-endian in Atlas), set this value to true and reach out to the Realm support team (https://support.mongodb.com) for help with migrating your data to the new format.

Methods

Add<T>(IEnumerable<T>, bool)

Add a collection of standalone RealmObjects to this Realm.

Declaration

public void Add<T>(IEnumerable<T> objs, bool update = false) where T : IRealmObject

Parameters

Type	Name	Description
IEnumerable<T>	objs	A collection of IRealmObject instances that will be added to this Realm.
bool	update	If true, and an object with the same primary key already exists, performs an update.

Type Parameters

Name	Description
T	The Type T must not only be a IRealmObject but also have been processed by the Fody weaver, so it has persistent properties.

Remarks

If the collection contains items that are already managed by this Realm, they will be ignored. This method modifies the objects in-place, meaning that after it has run, all items in objs will be managed.

Exceptions

Type	Condition
RealmInvalidTransactionException	If you invoke this when there is no write Transaction active on the Realm.
RealmObjectManagedByAnotherRealmException	You can't manage an object with more than one Realm.

Add<T>(T, bool)

This Realm will start managing an IRealmObject which has been created as a standalone object.

Declaration

public T Add<T>(T obj, bool update = false) where T : IRealmObject

Parameters

Type	Name	Description
T	obj	Must be a standalone object, null not allowed.
bool	update	If true, and an object with the same primary key already exists, performs an update.

Returns

Type	Description
T	The passed object, so that you can write var person = realm.Add(new Person { Id = 1 });.

Type Parameters

Name	Description
T	The Type T must not only be a IRealmObject but also have been processed by the Fody weaver, so it has persistent properties.

Remarks

If the object is already managed by this Realm, this method does nothing. This method modifies the object in-place, meaning that after it has run, obj will be managed. Returning it is just meant as a convenience to enable fluent syntax scenarios.

Exceptions

Type	Condition
RealmInvalidTransactionException	If you invoke this when there is no write Transaction active on the Realm.
RealmObjectManagedByAnotherRealmException	You can't manage an object with more than one Realm.

All<T>()

Extract an iterable set of objects for direct use or further query.

Declaration

public IQueryable<T> All<T>() where T : IRealmObject

Returns

Type	Description
IQueryable<T>	A queryable collection that without further filtering, allows iterating all objects of class T, in this Realm.

Type Parameters

Name	Description
T	The Type T must be an IRealmObject.

Remarks

The returned collection is evaluated lazily and no objects are being held in memory by the collection itself, which means this call is very cheap even for huge number of items.

BeginWrite()

Begins a write transaction for this Realm.

Declaration

public Transaction BeginWrite()

Returns

Type	Description
Transaction	A transaction in write mode, which is required for any creation or modification of objects persisted in a Realm.

Examples

using (var trans = realm.BeginWrite())
{
    realm.Add(new Dog
    {
        Name = "Rex"
    });
    trans.Commit();
}

BeginWriteAsync(CancellationToken)

Asynchronously begins a write transaction for this Realm.

Declaration

public Task<Transaction> BeginWriteAsync(CancellationToken cancellationToken = default)

Parameters

Type	Name	Description
CancellationToken	cancellationToken	Optional cancellation token to stop waiting to start a write transaction.

Returns

Type	Description
Task<Transaction>	An awaitable Task that returns a transaction in write mode. A transaction is required for any creation, deletion or modification of objects persisted in a Realm.

Remarks

This method asynchronously acquires the write lock and then dispatches the continuation on the original thread the Realm was opened on. The transaction can then be committed either asynchronously or synchronously.
When invoked on a thread without SynchronizationContext (i.e. typically background threads), this method calls BeginWrite() and executes synchronously.

Examples

using (var trans = await realm.BeginWriteAsync())
{
    realm.Add(new Dog
    {
        Name = "Rex"
    });
    await trans.CommitAsync();
    // or just
    // trans.Commit();
}

Compact(RealmConfigurationBase?)

Compacts a Realm file. A Realm file usually contains free/unused space. This method removes this free space and the file size is thereby reduced. Objects within the Realm file are untouched.

Declaration

public static bool Compact(RealmConfigurationBase? config = null)

Parameters

Type	Name	Description
RealmConfigurationBase	config	Optional configuration.

Returns

Type	Description
bool	true if successful, false if any file operation failed.

Remarks

The realm file must not be open on other threads. The file system should have free space for at least a copy of the Realm file. This method must not be called inside a transaction. The Realm file is left untouched if any file operation fails.

DeleteRealm(RealmConfigurationBase)

Deletes all files associated with a given Realm if the Realm exists and is not open.

Declaration

public static void DeleteRealm(RealmConfigurationBase configuration)

Parameters

Type	Name	Description
RealmConfigurationBase	configuration	A RealmConfigurationBase which supplies the realm path.

Remarks

The Realm file must not be open on other threads.
All but the .lock file will be deleted by this.

Exceptions

Type	Condition
RealmInUseException	Thrown if the Realm is still open.

Dispose()

Disposes the current instance and closes the native Realm if this is the last remaining instance holding a reference to it.

Declaration

public void Dispose()

Find<T>(ObjectId?)

Fast lookup of an object from a class which has a PrimaryKey property.

Declaration

public T? Find<T>(ObjectId? primaryKey) where T : IRealmObject

Parameters

Type	Name	Description
ObjectId?	primaryKey	Primary key to be matched exactly, same as an == search.

Returns

Type	Description
T	null or an object matching the primary key.

Type Parameters

Name	Description
T	The Type T must be a IRealmObject.

Exceptions

Type	Condition
RealmClassLacksPrimaryKeyException	If the IRealmObject class T lacks PrimaryKeyAttribute.

Find<T>(Guid?)

Fast lookup of an object from a class which has a PrimaryKey property.

Declaration

public T? Find<T>(Guid? primaryKey) where T : IRealmObject

Parameters

Type	Name	Description
Guid?	primaryKey	Primary key to be matched exactly, same as an == search.

Returns

Type	Description
T	null or an object matching the primary key.

Type Parameters

Name	Description
T	The Type T must be a IRealmObject.

Exceptions

Type	Condition
RealmClassLacksPrimaryKeyException	If the IRealmObject class T lacks PrimaryKeyAttribute.

Find<T>(long?)

Fast lookup of an object from a class which has a PrimaryKey property.

Declaration

public T? Find<T>(long? primaryKey) where T : IRealmObject

Parameters

Type	Name	Description
long?	primaryKey	Primary key to be matched exactly, same as an == search. An argument of type long? works for all integer properties, supported as PrimaryKey.

Returns

Type	Description
T	null or an object matching the primary key.

Type Parameters

Name	Description
T	The Type T must be a IRealmObject.

Exceptions

Type	Condition
RealmClassLacksPrimaryKeyException	If the IRealmObject class T lacks PrimaryKeyAttribute.

Find<T>(string?)

Fast lookup of an object from a class which has a PrimaryKey property.

Declaration

public T? Find<T>(string? primaryKey) where T : IRealmObject

Parameters

Type	Name	Description
string	primaryKey	Primary key to be matched exactly, same as an == search.

Returns

Type	Description
T	null or an object matching the primary key.

Type Parameters

Name	Description
T	The Type T must be a IRealmObject.

Exceptions

Type	Condition
RealmClassLacksPrimaryKeyException	If the IRealmObject class T lacks PrimaryKeyAttribute.

Freeze()

Returns a frozen (immutable) snapshot of this Realm.

A frozen Realm is an immutable snapshot view of a particular version of a Realm's data. Unlike normal Realm instances, it does not live-update to reflect writes made to the Realm, and can be accessed from any thread. Writing to a frozen Realm is not allowed, and attempting to begin a write transaction will throw an exception.

All objects and collections read from a frozen Realm will also be frozen.

Note: Keeping a large number of frozen Realms with different versions alive can have a negative impact on the filesize of the underlying database. In order to avoid such a situation it is possible to set MaxNumberOfActiveVersions.

Declaration

public Realm Freeze()

Returns

Type	Description
Realm	A frozen Realm instance.

GetInstance(RealmConfigurationBase?)

Factory for obtaining a Realm instance for this thread.

Declaration

public static Realm GetInstance(RealmConfigurationBase? config = null)

Parameters

Type	Name	Description
RealmConfigurationBase	config	Optional configuration.

Returns

Type	Description
Realm	A Realm instance.

Exceptions

Type	Condition
RealmFileAccessErrorException	Thrown if the file system returns an error preventing file creation.

GetInstance(string)

Factory for obtaining a Realm instance for this thread.

Declaration

public static Realm GetInstance(string databasePath)

Parameters

Type	Name	Description
string	databasePath	Path to the realm, must be a valid full path for the current platform, relative subdirectory, or just filename.

Returns

Type	Description
Realm	A Realm instance.

Remarks

If you specify a relative path, sandboxing by the OS may cause failure if you specify anything other than a subdirectory.

Exceptions

Type	Condition
RealmFileAccessErrorException	Thrown if the file system returns an error preventing file creation.

GetInstanceAsync(RealmConfigurationBase?, CancellationToken)

Factory for asynchronously obtaining a Realm instance.

Declaration

public static Task<Realm> GetInstanceAsync(RealmConfigurationBase? config = null, CancellationToken cancellationToken = default)

Parameters

Type	Name	Description
RealmConfigurationBase	config	A configuration object that describes the realm.
CancellationToken	cancellationToken	An optional cancellation token that can be used to cancel the work.

Returns

Type	Description
Task<Realm>	An awaitable Task<TResult> that is completed once the remote realm is fully synchronized or after migrations are executed if it's a local realm.

Remarks

This method will perform any migrations on a background thread before returning an opened instance to the calling thread.

IsSameInstance(Realm)

Determines whether this instance is the same core instance as the passed in argument.

Declaration

public bool IsSameInstance(Realm other)

Parameters

Type	Name	Description
Realm	other	The Realm to compare with the current Realm.

Returns

Type	Description
bool	true if this instance is the same core instance; otherwise, false.

Remarks

You can, and should, have multiple instances open on different threads which have the same path and open the same Realm.

Refresh()

Update the Realm instance and outstanding objects to point to the most recent persisted version.

Declaration

public bool Refresh()

Returns

Type	Description
bool	Whether the Realm had any updates. Note that this may return true even if no data has actually changed.

RefreshAsync()

Asynchronously wait for the Realm instance and outstanding objects to get updated to point to the most recent persisted version.

Declaration

public Task<bool> RefreshAsync()

Returns

Type	Description
Task<bool>	Whether the Realm had any updates. Note that this may return true even if no data has actually changed.

Remarks

On worker threads (where the SynchronizationContext) is null, this will call the blocking Refresh() method instead. On the main thread (or other threads that have SynchronizationContext), this will wait until the instance automatically updates to resolve the task. Note that you must keep a reference to the Realm until the returned task is resolved.

Remove(IRealmObjectBase)

Removes a persistent object from this Realm, effectively deleting it.

Declaration

public void Remove(IRealmObjectBase obj)

Parameters

Type	Name	Description
IRealmObjectBase	obj	Must be an object persisted in this Realm.

Exceptions

Type	Condition
RealmInvalidTransactionException	If you invoke this when there is no write Transaction active on the Realm.
ArgumentNullException	If obj is null.
ArgumentException	If you pass an unmanaged object.

RemoveAll()

Remove all objects of all types managed by this Realm.

Declaration

public void RemoveAll()

Exceptions

Type	Condition
RealmInvalidTransactionException	If you invoke this when there is no write Transaction active on the Realm.

RemoveAll<T>()

Remove all objects of a type from the Realm.

Declaration

public void RemoveAll<T>() where T : IRealmObject

Type Parameters

Name	Description
T	Type of the objects to remove.

Exceptions

Type	Condition
RealmInvalidTransactionException	If you invoke this when there is no write Transaction active on the Realm.
ArgumentException	If the type T is not part of the limited set of classes in this Realm's Schema.

RemoveRange<T>(IQueryable<T>)

Remove objects matching a query from the Realm.

Declaration

public void RemoveRange<T>(IQueryable<T> range) where T : IRealmObjectBase

Parameters

Type	Name	Description
IQueryable<T>	range	The query to match for.

Type Parameters

Name	Description
T	Type of the objects to remove.

Exceptions

Type	Condition
RealmInvalidTransactionException	If you invoke this when there is no write Transaction active on the Realm.
ArgumentException	If range is not the result of All<T>() or subsequent LINQ filtering.
ArgumentNullException	If range is null.

ResolveReference<TValue>(Dictionary<TValue>)

Returns the same collection as the one referenced when the ThreadSafeReference.Dictionary<TValue> was first created, but resolved for the current Realm for this thread.

Declaration

public IDictionary<string, TValue>? ResolveReference<TValue>(ThreadSafeReference.Dictionary<TValue> reference)

Parameters

Type	Name	Description
ThreadSafeReference.Dictionary<TValue>	reference	The thread-safe reference to the thread-confined IDictionary<TKey, TValue> to resolve in this Realm.

Returns

Type	Description
IDictionary<string, TValue>	A thread-confined instance of the original IDictionary<TKey, TValue> resolved for the current thread or null if the dictionary's parent object has been deleted after the reference was created.

Type Parameters

Name	Description
TValue	The type of the values contained in the dictionary.

ResolveReference<T>(List<T>)

Returns the same collection as the one referenced when the ThreadSafeReference.List<T> was first created, but resolved for the current Realm for this thread.

Declaration

public IList<T>? ResolveReference<T>(ThreadSafeReference.List<T> reference)

Parameters

Type	Name	Description
ThreadSafeReference.List<T>	reference	The thread-safe reference to the thread-confined IList<T> to resolve in this Realm.

Returns

Type	Description
IList<T>	A thread-confined instance of the original IList<T> resolved for the current thread or null if the list's parent object has been deleted after the reference was created.

Type Parameters

Name	Description
T	The type of the objects, contained in the collection.

ResolveReference<T>(Object<T>)

Returns the same object as the one referenced when the ThreadSafeReference.Object<T> was first created, but resolved for the current Realm for this thread.

Declaration

public T? ResolveReference<T>(ThreadSafeReference.Object<T> reference) where T : IRealmObjectBase

Parameters

Type	Name	Description
ThreadSafeReference.Object<T>	reference	The thread-safe reference to the thread-confined IRealmObject/IEmbeddedObject to resolve in this Realm.

Returns

Type	Description
T	A thread-confined instance of the original IRealmObject/IEmbeddedObject resolved for the current thread or null if the object has been deleted after the reference was created.

Type Parameters

Name	Description
T	The type of the object, contained in the reference.

ResolveReference<T>(Query<T>)

Returns the same query as the one referenced when the ThreadSafeReference.Query<T> was first created, but resolved for the current Realm for this thread.

Declaration

public IQueryable<T> ResolveReference<T>(ThreadSafeReference.Query<T> reference) where T : IRealmObjectBase

Parameters

Type	Name	Description
ThreadSafeReference.Query<T>	reference	The thread-safe reference to the thread-confined IQueryable<T> to resolve in this Realm.

Returns

Type	Description
IQueryable<T>	A thread-confined instance of the original IQueryable<T> resolved for the current thread.

Type Parameters

Name	Description
T	The type of the object, contained in the query.

ResolveReference<T>(Set<T>)

Returns the same collection as the one referenced when the ThreadSafeReference.Set<T> was first created, but resolved for the current Realm for this thread.

Declaration

public ISet<T>? ResolveReference<T>(ThreadSafeReference.Set<T> reference)

Parameters

Type	Name	Description
ThreadSafeReference.Set<T>	reference	The thread-safe reference to the thread-confined ISet<T> to resolve in this Realm.

Returns

Type	Description
ISet<T>	A thread-confined instance of the original ISet<T> resolved for the current thread or null if the set's parent object has been deleted after the reference was created.

Type Parameters

Name	Description
T	The type of the elements, contained in the collection.

Write(Action)

Execute an action inside a temporary Transaction. If no exception is thrown, the Transaction will be committed.

Declaration

public void Write(Action action)

Parameters

Type	Name	Description
Action	action	Action to execute inside a Transaction, creating, updating, or removing objects.

Remarks

Creates its own temporary Transaction and commits it after running the lambda passed to action. Be careful of wrapping multiple single property updates in multiple Write(Action) calls. It is more efficient to update several properties or even create multiple objects in a single Write(Action), unless you need to guarantee finer-grained updates.

Examples

realm.Write(() =>
{
    realm.Add(new Dog
    {
        Name = "Eddie",
        Age = 5
    });
});

WriteAsync(Action, CancellationToken)

Execute an action inside a temporary Transaction. If no exception is thrown, the Transaction will be committed. If the method is not called from a thread with a SynchronizationContext (like the UI thread), it behaves synchronously.

Declaration

public Task WriteAsync(Action action, CancellationToken cancellationToken = default)

Parameters

Type	Name	Description
Action	action	Action to execute inside a Transaction, creating, updating, or removing objects.
CancellationToken	cancellationToken	Optional cancellation token to stop waiting to start a write transaction.

Returns

Type	Description
Task	An awaitable Task that indicates that the transaction has been committed successfully.

Examples

await realm.WriteAsync(() =>
{
    realm.Add(new Dog
    {
        Breed = "Dalmatian",
    });
});

WriteAsync<T>(Func<T>, CancellationToken)

Execute a delegate inside a temporary Transaction. If no exception is thrown, the Transaction will be committed. If the method is not called from a thread with a SynchronizationContext (like the UI thread), it behaves synchronously.

Declaration

public Task<T> WriteAsync<T>(Func<T> function, CancellationToken cancellationToken = default)

Parameters

Type	Name	Description
Func<T>	function	Delegate with one return value to execute inside a Transaction, creating, updating, or removing objects.
CancellationToken	cancellationToken	Optional cancellation token to stop waiting to start a write transaction.

Returns

Type	Description
Task<T>	An awaitable Task that indicates that the transaction has been committed successfully. The result of the task is the result returned by invoking function.

Type Parameters

Name	Description
T	The type returned by the input delegate.

Examples

var dog = await realm.WriteAsync(() =>
{
    return realm.Add(new Dog
    {
        Breed = "Dalmatian",
    });
});

WriteCopy(RealmConfigurationBase)

Writes a compacted copy of the Realm to the path in the specified config. If the configuration object has non-null EncryptionKey, the copy will be encrypted with that key.

Declaration

public void WriteCopy(RealmConfigurationBase config)

Parameters

Type	Name	Description
RealmConfigurationBase	config	Configuration, specifying the path and optionally the encryption key for the copy.

Remarks

1. The destination file cannot already exist.
2. When using a local Realm and this is called from within a transaction it writes the current data, and not the data as it was when the last transaction was committed.

Write<T>(Func<T>)

Execute a delegate inside a temporary Transaction. If no exception is thrown, the Transaction will be committed.

Declaration

public T Write<T>(Func<T> function)

Parameters

Type	Name	Description
Func<T>	function	Delegate with one return value to execute inside a Transaction, creating, updating, or removing objects.

Returns

Type	Description
T	The return value of function.

Type Parameters

Name	Description
T	The type returned by the input delegate.

Remarks

Creates its own temporary Transaction and commits it after running the lambda passed to function. Be careful of wrapping multiple single property updates in multiple Write(Action) calls. It is more efficient to update several properties or even create multiple objects in a single Write(Action), unless you need to guarantee finer-grained updates.

Examples

var dog = realm.Write(() =>
{
    return realm.Add(new Dog
    {
        Name = "Eddie",
        Age = 5
    });
});

Events

Error

Triggered when a Realm-level exception has occurred.

Declaration

public event EventHandler<ErrorEventArgs>? Error

Event Type

Type	Description
EventHandler<ErrorEventArgs>

RealmChanged

Triggered when a Realm has changed (i.e. a Transaction was committed).

Declaration

public event Realm.RealmChangedEventHandler? RealmChanged

Event Type

Type	Description
Realm.RealmChangedEventHandler

Implements

IDisposable