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A newer version of this LINQ to SQL template is available.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 file, choose Properties and set the Custom Tool to blank
  • Rename 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. 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


10 responses

  1. Avatar for Nikhil Kothari

    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?

    Nikhil Kothari August 7, 2008
  2. Avatar for Damien Guard

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

    Damien Guard August 7, 2008
  3. Avatar for Jon Kruger

    I've always wished that I could modify the L2S code generator. Looking forward to checking it out.

    Jon Kruger August 10, 2008
  4. Avatar for Rybolt

    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 :)

    Rybolt August 26, 2008
  5. Avatar for Damien Guard

    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.

    Damien Guard August 26, 2008
  6. Avatar for Spencer

    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?

    Spencer August 26, 2008
  7. Avatar for Damien Guard

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

    Damien Guard August 26, 2008
  8. Avatar for Tor Christian

    I would very much like a 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 :)

    Tor Christian August 28, 2008
  9. Avatar for LINQ Junkie

    This article shows how it's done, but based on a different technology:

    As about VB, the site the article refers to has a VB implementation, but implementing only scenario 3 as described by the article.

    LINQ Junkie December 20, 2008
  10. Avatar for Nithin Mohan T K

    that coolest and easiest linq2sql code generator t4 template. really thanks..

    really use ful for all of us..

    Nithin Mohan T K March 14, 2010