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Insert, Update, and Delete Operations (LINQ to SQL)

  • Artykuł

You perform Insert, Update, and Delete operations in LINQ to SQL by adding, changing, and removing objects in your object model. By default, LINQ to SQL translates your actions to SQL and submits the changes to the database.

LINQ to SQL offers maximum flexibility in manipulating and persisting changes that you made to your objects. As soon as entity objects are available (either by retrieving them through a query or by constructing them anew), you can change them as typical objects in your application. That is, you can change their values, you can add them to your collections, and you can remove them from your collections. LINQ to SQL tracks your changes and is ready to transmit them back to the database when you call SubmitChanges.

Note

LINQ to SQL does not support or recognize cascade-delete operations. If you want to delete a row in a table that has constraints against it, you must either set the ON DELETE CASCADE rule in the foreign-key constraint in the database, or use your own code to first delete the child objects that prevent the parent object from being deleted. Otherwise, an exception is thrown. For more information, see How to: Delete Rows From the Database (LINQ to SQL).

The following excerpts use the Customer and Order classes from the Northwind sample database. Class definitions are not shown for brevity.

Dim db As New Northwnd("…\Northwnd.mdf")

Dim cust As Customer = _
(From c In db.Customers _
Where c.CustomerID = "ALFKI" _
Select c) _
.First()

' Change the name of the contact.
cust.ContactName = "New Contact" 

' Create and add a new Order to Orders collection. 
Dim ord As New Order With {.OrderDate = DateTime.Now}
cust.Orders.Add(ord)

' Delete an existing Order. 
Dim ord0 As Order = cust.Orders(0)

' Removing it from the table also removes it from  
' the Customer’s list.
db.Orders.DeleteOnSubmit(ord0)

' Ask the DataContext to save all the changes.
db.SubmitChanges()

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

// Query for a specific customer. 
var cust =
    (from c in db.Customers
     where c.CustomerID == "ALFKI" 
     select c).First();

// Change the name of the contact.
cust.ContactName = "New Contact";

// Create and add a new Order to the Orders collection.
Order ord = new Order { OrderDate = DateTime.Now };
cust.Orders.Add(ord);

// Delete an existing Order.
Order ord0 = cust.Orders[0];

// Removing it from the table also removes it from the Customer’s list.
db.Orders.DeleteOnSubmit(ord0);

// Ask the DataContext to save all the changes.
db.SubmitChanges();

When you call SubmitChanges, LINQ to SQL automatically generates and executes the SQL commands that it must have to transmit your changes back to the database.

Note

You can override this behavior by using your own custom logic, typically by way of a stored procedure. For more information, see Responsibilities of the Developer In Overriding Default Behavior (LINQ to SQL).

Developers using Visual Studio can use the Object Relational Designer to develop stored procedures for this purpose. Object Relational Designer (O/R Designer)
Object Relational Designer (O/R Designer)

See Also

Concepts

Downloading Sample Databases (LINQ to SQL)

Other Resources

Customizing Insert, Update, and Delete Operations (LINQ to SQL)