DataContext.GetChangeSet Method

Definition

Namespace:

System.Data.Linq

Assembly:

System.Data.Linq.dll

Gets the modified objects tracked by DataContext.

public:
 System::Data::Linq::ChangeSet ^ GetChangeSet();

public System.Data.Linq.ChangeSet GetChangeSet ();

member this.GetChangeSet : unit -> System.Data.Linq.ChangeSet

Public Function GetChangeSet () As ChangeSet

Returns

ChangeSet

The set of objects is returned as three read-only collections.

Examples

Northwnd db = new Northwnd(@"c:\northwnd.mdf");

var custQuery =
    from cust in db.Customers
    where cust.City == "London"
    select cust;

foreach (Customer custObj in custQuery)
{
    Console.WriteLine("CustomerID: {0}", custObj.CustomerID);
    Console.WriteLine("\tOriginal value: {0}", custObj.City);
    custObj.City = "Paris";
    Console.WriteLine("\tUpdated value: {0}", custObj.City);
}

ChangeSet cs = db.GetChangeSet();
Console.Write("Total changes: {0}", cs);
// Freeze the console window.
Console.ReadLine();

db.SubmitChanges();

Dim db As New Northwnd("c:\northwnd.mdf")

Dim custQuery = _
    From cust In db.Customers _
    Where (cust.City = "London") _
    Select cust

For Each custObj As Customer In custQuery
    Console.WriteLine("CustomerID: {0}", custObj.CustomerID)
    Console.WriteLine(vbTab & "Original value: {0}", custObj.City)
    custObj.City = "Paris"
    Console.WriteLine(vbTab & "Updated value: {0}", custObj.City)
Next

Dim cs As ChangeSet = db.GetChangeSet()
Console.Write("Total changes: {0}", cs)
' Freeze the console window.
Console.ReadLine()

db.SubmitChanges()

Remarks

Note the following considerations:

• GetChangeSet might have side effects, such as inference of insert and delete operations that are usually performed at the time of SubmitChanges. For example, objects that are used in the following operations can create corresponding inferred operations in the following list:

  • Add to InsertOnSubmit.

  • EntityRef<TEntity> assignment to null (possibly because of Remove to DeleteOnSubmit.

• The set may not be ordered according to foreign key constraints.

• Database-generated values (for example, primary and foreign key values, timestamps, and so forth) are not available. Such information requires database command execution and perhaps the propagation of retrieved information (for example, foreign key from primary key).

• The set of changed objects is computed at the time of the call. Subsequent calls to SubmitChanges can produce a different set if additional changes are made.

Output when no changes have been made appears as follows:

{Added: 0, Removed: 0, Modified: 0}