如何获取自动生成的ID？

Question

System
Language:C#
Database:SQL
IDE:C# Express 2010

I have a User object/class and db table. The user has multiple Adresses and I have already defined the Addresses table, how do I add and commit the address to the DB

I have created an Add function for the User (see below) The User class holds a List addresses

User Class

int id
string name
List<Address> adresses

Table User

id
name
addresses

Table Addresses

id 
address
user_id (FK)

I have the Add function in the User class to add User Objects, I stripped out the handling code to make it clearer on SO.

My question is, how do I get the id of the User just added and add the Address into the database. And How do I define the FK on the Address Table

 class User {

    public static bool Add(User user, UserOptions option = UserOptions.System)
    {
        //Instantiate the  DataClassesDataContext
        var db = DBContext.Create();

        //Make Sure User does not exist
        //returns true if no existing user
        if (Users.validateForAdd(user))
        {
           //Now add
           db.Users.InsertOnSubmit(user);

           //I assume I would get the id of the user just added but not sure how I do that

           db.SubmitChanges();
           return true;
        }

        //Failed to add
        return false;
    }

Final Solution

Just thought I would post the final solution from the below answers and comments.

//
// Creating and setting the Objects
//
User user = new User(name="john doe");
EntitySet < Address >  adressList = new EntitySet<Address>();

adressList.Add(new Address("Residential Home");
adressList.Add(new Address("Holiday Home...");

user.address = adressList;

//
//Persisting to the DB
//
var db = new DataContext();
db.Results.InsertOnSubmit(result);
db.SubmitChanges();

Answer 1

You can do one change to the above method Add. Instead of returning bool, you can return type int.

public static int Add(User user, UserOptions option = UserOptions.System)
 //Make Sure User does not exist
 //returns true if no existing user
 if (Users.validateForAdd(user))
 {
    ....
    ....
    //Instead of returning true you can return user.id
    return user.id;
 }
    //Instead of returning false you can return default value -1
    return -1;

}

So you can get the newly added user's id by calling method Add of User class and you can use that id to create List of addresses for the user.

Answer 2

My question is, how do I get the id of the User just added and add the Address into the database.

The key is that you do not need it . Instead of assigning a foreign key field with an id, in Linq-2-sql you assign entities to eachother.

So instead of doing

somerelated_table.fk_user_id = user.id

you do

somerelated_table.user = user

Linq-2-sql will handle the proper assignment of the user.id when you call SubmitChanges. Plus as a bonus it will all be done in a single transaction. That is the beauty of linq-2-sql.