Best thing about running One .Net Way is interaction with members of developer community. I thoroughly enjoy answering questions which come my way through this site. Early in the morning today I saw a question by Joey. To avoid loosing details in paraphrasing, here is the exact question asked by Joey.

I’m new to LINQ. If I had two tables “Customer” and “CustomerDetails”, how (using LINQ) can I insert to both of these tables? Do I need to create a “Customer” object as well as a “CustomerDetails” object?

In short the answer is yes. LINQ can insert to both tables, you will need to populate both Customer and CustomerDetails objects with data. I will now present an example to support my answer.

What we have here is a one to many scenario which involves two tables linked through a Foreign Key. To serve as an example, I have modelled the tables like this.

Each customer can have many nick names which are stored in CustomerDetails table. Let’s go ahead and generate LINQ To SQL entities. Please refer to LINQ To SQL tutorial if you want a refresher on how to generate LINQ To SQL entities. After dragging our tables to designer we can see that designer has recognised relationship we have between our tables.

A quick glance over generated code confirms that we have a property of Type EntitySet<CustomerDetails> in our Customer class.

Now let’s insert some data. The following code will insert one Customer record and two CustomerDetails records.

private void InsertData()
{
  string firstName = "LINQ";
  string lastName = "Dude";
  string nickName1 = "Cool";
  string nickName2 = "DataBuster";

  using (CustomerDatabaseDataContext context = new CustomerDatabaseDataContext())
  {
    // Create a Customer object
    Customer customer = new Customer
      {
        FirstName = firstName,
        LastName = lastName,
        // Create two CustomerDetails objects
        CustomerDetails = new System.Data.Linq.EntitySet<CustomerDetail>()
          {
            new CustomerDetail{NickName = nickName1},
            new CustomerDetail{NickName = nickName2}
          }

        };

    // We'd like to Insert our changes as new
    context.Customers.InsertOnSubmit(customer);
    // Submit changes to database
    context.SubmitChanges();
  }
}

Code above produces following T-SQL

exec sp_executesql N'INSERT INTO [dbo].[Customer]([FirstName], [LastName])
VALUES (@p0, @p1)

SELECT CONVERT(Int,SCOPE_IDENTITY()) AS [value]',N'@p0 varchar(4),@p1 varchar(4)',
@p0='LINQ',@p1='Dude'
go
exec sp_executesql N'INSERT INTO [dbo].[CustomerDetails]([CustomerId], [NickName])
VALUES (@p0, @p1)

SELECT CONVERT(Int,SCOPE_IDENTITY()) AS [value]',N'@p0 int,@p1 varchar(4)',
@p0=2,@p1='Cool'
go
exec sp_executesql N'INSERT INTO [dbo].[CustomerDetails]([CustomerId], [NickName])
VALUES (@p0, @p1)

SELECT CONVERT(Int,SCOPE_IDENTITY()) AS [value]',N'@p0 int,@p1 varchar(10)',
@p0=2,@p1='DataBuster'
go

In T-SQL above you can see that we are inserting one row for Customer and two rows for CustomerDetails. However in our C# we only called SubmitChanges once.