Книга: C# 2008 Programmer

Inserting New Rows

Inserting New Rows

To insert a row into a table, use the InsertOnSubmit() method. For example, the following code inserts a new author into the authors table:

DataClasses1DataContext database = new DataClasses1DataContext();
author a = new author() {
 au_id = "789-12-3456",
 au_fname = "James",
 au_lname = "Bond",
 phone = "987654321"
};
//---record is saved to object model---
database.authors.InsertOnSubmit(a);

Note that the InsertOnSubmit() method only affects the object model; it does not save the changes back to the database. To save the changes back to the database, you need to use the SubmitChanges() method:

//---send changes to database---
database.SubmitChanges();

What happens when you need to insert a new book title from a new author? As you saw earlier, the titles table is related to the titleauthors via the title_id field, while the authors table is related to the titleauthors table via the author_id field. Therefore, if you insert a new row into the titles table, you need to insert a new row into the authors and titleauthors tables as well.

To do so, you first create a new author and title row:

DataClasses1DataContext database = new DataClasses1DataContext();
author a = new author() {
 au_id = "123-45-6789",
 au_fname = "Wei-Meng",
 au_lname = "Lee",
 phone = "123456789"
};
title t = new title() {
 title_id = "BU5555",
 title1 = "How to Motivate Your Employees",
 pubdate = System.DateTime.Now,
 type = "business"
};

Then, add a new titleauthor row by associating its author and title properties with the new title and author row you just created:

titleauthor ta = new titleauthor() {
 author = a,
 title = t
};

Finally, save the changes to the object model and submit the changes to the database:

//---record is saved to object model---
database.titleauthors.InsertOnSubmit(ta);
//---send changes to database---
database.SubmitChanges();

Notice that you do not need to worry about indicating the title_id and author_id fields in the titleauthors table; LINQ to SQL does those for you automatically.

Оглавление книги