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Saturday, September 02, 2006

Building and using a LINQ for SQL Class Library with ASP.NET 2.0

In my previous posts on doing data access using LINQ and ASP.NET, I used the built-in SQLMetal command-line utility to automatically generate the data model classes for my LINQ data classes.  Recently I've been using the LINQ for SQL (aka DLINQ) designer to define my data models instead, and have been really impressed with how easily it enables me to build a re-usable class library that nicely encapsulates my data and business logic.

The below walkthrough demonstrates how you can get started with it yourself.  Simply install the LINQ May CTP download on top of VS 2005, and you can then follow along all of the steps below yourself.  For the sample below I am using C#, but everything works equally well in VB as well.

Step 1: Create a New LINQ Enabled Class Library

Choose File->New Project within Visual Studio and navigate to the "LINQ Preview" node in the project-type tree-explorer.  Then select the "LINQ Library" project icon and create a new LINQ enabled class library:

This will create a class library project whose MSBuild project file enables compilation support for LINQ.  A default "Class1.cs" file is added to the project -- I recommend just deleting it to start with an empty project.

Step 2: Add a LINQ for SQL Data Model to the Project

Right-click on the project and choose the Add->New Item context menu item.  Scroll down in the dialog and select the "DLINQ Object" icon, and give it an appropriate name (in this sample I'm naming it "Northwind" since I'm going to be modeling the Northwind database):


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