Attach(TEntity,TEntity) Method

In This Topic

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

Syntax

Visual Basic
C#

'Declaration
 
Public Overloads Sub Attach( _
   ByVal entity As TEntity, _
   ByVal original As TEntity _
)

public void Attach( 
   TEntity entity,
   TEntity original
)

Parameters

entity: The entity to be attached.
original: An instance of the same entity type with data members that contain the original values.

Remarks

In the following example, the Customer object is already correctly configured. You can call Attach without having to replay the updates. 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.

Example

The following example shows how the collection can be iterated over to retrieve conflict information.

Optimistic Concurrency: Overview

csharp

using (Northwnd db2 = new Northwnd(@"c:\northwnd.mdf"))
{
Customer Cust_File = new Customer();
string xmlFile = "";

    // Get the original object from the deserializer.
Customer c = SerializeHelper.Deserialize
        (xmlFile, Cust_File);

    // Set all the desired properties to the entity to be attached.
Customer c_updated = new Customer() { CustomerID = c.CustomerID,
        Phone = "425-123-4567", CompanyName = "Microsoft" };
    db2.Customers.Attach(c_updated, c);

    // Perform last minute updates, which will still take effect. 
    c_updated.Phone = "425-765-4321";

    // SubmitChanges()sets the phoneNumber and CompanyName of
    // customer with customerID=Cust. to "425-765-4321" and
    // "Microsoft" respectively.
    db2.SubmitChanges();  
}

Visual Basic

Using db = New Northwnd("...")
Dim Cust_File As New Customer()
Dim xmlFile As String = ""

    'Get the original object from the deserializer.
Dim c As Customer = SerializeHelper.Deserialize(Of Customer)(xmlFile, Cust_File)

    ' Set all the desired properties to the entity to be attached.
Dim c_updated As New Customer With {.CustomerID = c.CustomerID, _
.Phone = "425-123-4567", .CompanyName = "Microsoft"}
    db.Customers.Attach(c_updated, c)

    ' Perform last minute updates, which will still take effect. 
c_updated.Phone = "425-765-4321"

    ' SubmitChanges()sets the phoneNumber and CompanyName of
    ' customer with customerID=Cust. to "425-765-4321" and
    ' "Microsoft" respectively.
    db.SubmitChanges()
End Using

Requirements

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference

Table<TEntity> Class
Table<TEntity> Members
Overload List

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