LINQ to SQL T4 template reloaded

A newer version of this LINQ to SQL template is available.

The topic of modifying the code generation phase of LINQ to SQL comes up quite often and the limited T4 template I published here last month was good at showing the potential but wasn’t a practical replacement for the code generation phase.

I am please to make available the next version, which now…

Runs from the DBML therefore keeping the designer in the loop
Generate all the attributes for columns and tables including UpdateCheck, IsDbGenerated etc.
Supports associations including those with a foreign key
Generates appropriate attributes and code for both serialization modes

In short it generates code that is now functionally equivalent to SQL Metal with the following caveats:

C# only – VB.NET can be added if there is some interest
Stored procedures – not yet supported
Table inheritance - incomplete
DBML changes require you open and re-save the T4 template so it regenerates the code
Unidirectional serialization requires you add System.Runtime.Serialization to your project references (thanks Roger!)

To use the template :

Extract the archive and add the two files to your project
Right-click on the L2ST4.tt file, choose Properties and set the Custom Tool to blank
Rename DataClasses1.tt to the same name as your DBML file (but keeping the .tt extension) and open it
Click save and watch a freshly generate C# DataContext pop out
Switch off the LINQ to SQL designer generated C# by either setting the Custom Tool on the DBML to blank or setting the Build Action on the generated C# to None.

L2ST4.tt contains a lightweight wrapper around the DBML which is processed using LINQ to XML making the template easier to work with and providing a central for naming rules etc.

This code should be treated as a sample and hasn’t received much testing yet so feel free to leave comments or feedback here.

Some places you could take this template:

Generate an interface for your data context to improve mocking
Alternative naming and defaults
Splitting output into multiple files
New languages

[)amien

13 responses to “LINQ to SQL T4 template reloaded”

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1 Nikhil Kothari Aug 7th, 2008 at 21:08

I wonder if your code generator could be packaged into a VS code generator, and then someone can simply replace the default DBML code generator?
2 Damien Guard Aug 7th, 2008 at 23:08

I wouldn't know where to start with that but if you're offering to show me the way ;-)

[)amien
3 Jon Kruger Aug 10th, 2008 at 00:08

I've always wished that I could modify the L2S code generator. Looking forward to checking it out.
4 Rybolt Aug 26th, 2008 at 17:08

Thanks a lot for this template and t4 intro. I've been researching ways to customize LINQ to SQL generated code for a few days now. Ideally a good C# parser and CodeDOM could have been useful, but there is no good C# parser, at least an updated one.

It seems unfortunate that we can't use what sqlmetal gives us, and then use the template to alter it. Essentially having to recreate all that functionality to gain back control :)
5 Damien Guard Aug 26th, 2008 at 18:08

I would love to see the .NET Framework include parsers for C# and VB.NET although they would probably create a CodeDOM representation which is a very ugly and awkward to use API.

Thankfully the code-generation phase is relatively easy as this template shows and SqlMetal can take care of the trickier SQL to DBML phase.

[)amien
6 Spencer Aug 26th, 2008 at 22:08

I'm new to DSL, but when I try this out (I'm planning on making some modifications to your template), it fails because some of my dbml markup contains types that are enumerations in my project. Any suggestions or tips?
7 Damien Guard Aug 26th, 2008 at 22:08

I'm not sure I get what the error is - can you post the compilation error and a short snippet of the syntax?

[)amien
8 Tor Christian Aug 28th, 2008 at 10:08

I would very much like a vb.net version of the template :)

I am working on a case where I need to send linq objects via wcf services. I understand that after installing 3.5 sp1, wcf services supports bidirectional references. The problem is that the linq dbml generation does not support enityrefs on many:1 relationships. I was hoping that your template could solve this issue, because I need both 1:many and many:1 references :)

http://oakleafblog.blogspot.com/2008/07/bidirectional-serialization-of-linq-to.html
9 LINQ Junkie Dec 20th, 2008 at 12:12

This article shows how it's done, but based on a different technology:
http://www.codeproject.com/KB/linq/CustomizeLINQtoSQL.aspx
As about VB, the site the article refers to has a VB implementation, but implementing only scenario 3 as described by the article.