Attach Method

Table<TEntity>.Attach Method

 

Attaches an entity to the DataContext.

Namespace:   System.Data.Linq
Assembly:  System.Data.Linq (in System.Data.Linq.dll)

NameDescription
System_CAPS_pubmethodAttach(TEntity)

Attaches a disconnected or "detached" entity to a new DataContext when original values are required for optimistic concurrency checks.

System_CAPS_pubmethodAttach(TEntity, TEntity)

Attaches an entity to the DataContext in either a modified or unmodified state by specifying both the entity and its original state.

System_CAPS_pubmethodAttach(TEntity, Boolean)

Attaches an entity to the DataContext in either a modified or unmodified state.

Use the Attach methods with entities that have been created in one DataContext, serialized to a client, and then deserialized back (with the intention to perform an update or delete operation). For more information, see Data Retrieval and CUD Operations in N-Tier Applications (LINQ to SQL).

Do not try to Attach an entity that has not been detached through serialization. Entities that have not been serialized still maintain associations with deferred loaders that can cause unexpected results if the entity becomes tracked by a second data context.

When a new entity is attached, deferred loaders for any child collections (for example, EntitySet collections of entities from associated tables) are initialized. When SubmitChanges is called, members of the child collections are put into an Unmodified state. To update members of a child collection, you must explicitly call Attach and specify that entity.

Attach attaches all entities in the object graph of the provided object. For example, the following C# code:

using (SampleDataContext db = new SampleDataContext()) {
    Employee employee = new Employee { employeeId = 1 };

    Master master = new Master();
    master.Employee = employee;

    Child child = new Child();
    child.Employee = employee;

    db.Employees.Attach(employee);

    master.Child = child;

    db.Masters.InsertOnSubmit(master);

    db.SubmitChanges();
}

The equivalent Visual Basic code is:

Using db As New SampleDataContext()    Dim employee As New Employee With { .employeeId = 1 }

    Dim master As New Master()
    master.Employee = employee

    Dim child As New Child()
    child.Employee = employee

    db.Employees.Attach(employee)

    master.Child = child

    db.Masters.InsertOnSubmit(master)

    db.SubmitChanges()

End Using

Calling Attach on Employee attaches employee, master, and child, because the Employee has relationships to both master and child. You must explicitly call InsertOnSubmit to change the state from attached to inserted.

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