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EntityReference<TEntity>.Attach Method

Creates a many-to-one or one-to-one relationship between two objects in the object context.

Namespace:  System.Data.Objects.DataClasses
Assembly:  System.Data.Entity (in System.Data.Entity.dll)

public void Attach(
	TEntity entity


Type: TEntity

The object being attached.


When the entity is null.


When the entity cannot be related to the current related end. This can occur when the association in the conceptual schema does not support a relationship between the two types.

The Attach method is used to define a relationship between an object and a related object when both objects are already attached to an object context. Set the related object to the Value property if the related object is not already attached to the object context. When both objects are detached, you can also define the relationship by setting the related object to the Value property and then attaching the root object in the object graph. For more information, see Attaching Objects (Entity Framework).

The object associated with this EntityReference<TEntity> and all objects being attached to it must be in an Unchanged or Modified state.

An object in the Deleted state can only be attached when the ObjectStateManager is already tracking the relationship instance.

.NET Framework

Supported in: 4.5, 4, 3.5 SP1

.NET Framework Client Profile

Supported in: 4

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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