LINQ to SQL XML Mapping Files

Most of the samples involving LINQ to SQL involve using the designer built-into Visual Studio 2008 since it’s very productive.  The LINQ to SQL designer is a great way to go and normally what I use when doing my ORM mapping.  I recently had someone ask if using the LINQ to SQL designer was required in order to leverage LINQ to SQL in their applications.  They had existing data entity classes that they wanted to use and didn’t want to re-create them using the designer.  In situations like this you can use built-in XML mapping features available in LINQ to SQL to get around using the designer if desired.  Going this route leads to writing more custom code and XML mapping files but also provides the ultimate in control especially if your data entity classes are created by another tool, you don’t want your classes littered with LINQ to SQL attributes, or you have some other reason for not wanting to use the designer.  In this article I’ll provide a step by step introduction to working with LINQ to SQL XML mapping files.

Step 1. Create the Data Entity Class

If you’re not using the LINQ to SQL designer then you’ll need to create your own data entity classes (or use a 3rd party tool to create them) that can hold data from the target database.  If you already have existing data entity classes that you want to use then you can skip this step.  Here’s a simple Customer class capable of holding some of the data found in the Customer table in theAdventureWorksLT database.  A diagram of the Customer table follows.

namespace Model
{
    public class Customer
    {
        public int CustomerID { get; set; }
        public string Title { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public DateTime ModifiedDate { get; set; }
    }
}