I have recently started work on what will become our first production application using LINQ-to-SQL and had hoped to use the CreateDatabase() function that is found on the generated DataContext to simplify the process of setting up the database on the client machine.
Ideally I wanted a nice simple piece of code like this
In this article I am going to look at Extension Methods. Although this is not a specific to LINQ post, Extension Methods are the compiler concept that LINQ was built on.
The basic premise is to allow the developer to add functionality to any class they like without the need to subclass it or wrap it in a wrapper class. This is a great new technique because it allows you to continue using a class like String or DateTime and not need to remember to use MyString and MyDateTime or fall back on static helper classes.
Next we are going to look at how you can use partial classes and partial methods to add functionality to your generated LINQ-to-SQL classes. One of the nice things about partial classes and the new partial methods is that you can extend the generated classes into a separate file that is not destroyed when you update the underlying data model. See my complaint here about other ways of changing the classes that does not have this benefit.
First things first is to create a new C# class file, I have called it AdventureWorks_Extra.cs to sort it below the AdventureWorks.dbml
One aspect of LINQ I have not covered yet is the equivalent of a GROUP BY in SQL. The GroupBy() function (which of course can be used from a LINQ expression as well as from the method syntax and I will show both) provides this functionality. One of the interesting things about grouping however is that there is a new interface introduced that you will want to understand, lets take a look at the method signature for GroupBy().
I have been looking at my web stats for the recent run of LINQ-to-SQL posts, and it seems a lot of people are making their way here from searches about some of the more standard features of LINQ-to-SQL. In the interest of addressing these visitors I am going to put together a post that covers the basics of data access.