The latest update to my template for generating LINQ to SQL classes from DBML is now available.
If you want to customize the LINQ to SQL code generation phase in your project without additional tool dependencies this could be what you’re looking for.
11 Dec 2008 Fixes to association code with one-to-one's and with no serialization required.
7 Dec 2008 Added IsDelayLoaded, IsUnique. Fixed association code, stored proc update overrides.
17 Nov 2008 Added IsInheritanceDefault read/emit IsDefault on type
26 Oct 2008 Emit column Name attribute if it doesn't match the member (thanks Steele)
20 Oct 2008 Handle class naming better, fix associations for renamed or out-of-sequence keys and their access modifiers
25 Sep 2008 Figure out missing association keys by using either sides primary key
25 Sep 2008 Empty DBML namespace is now no namespace instead of "MyApplication"
23 Sep 2008 fixed stored procedures with 0 parameters
22 Sep 2008 fixed VB.NET IsForeignKey attribute for associations
18 Sep 2008 now generates stored procedures including insert/update/delete with concurrency checking.
New since 'reloaded' version
- Inheritance - generates subclasses with all properties and code mappings.
- VB.NET - CSharpDataContext.tt is joined by a VB.NET emitting VBNetDataContext.tt.
- DataContract SP1 – additional mode to emit SP1-compatible DataContract serialization via Roger Jennings.
- Composite keys – both as the primary key and as a foreign key in an association.
- Type attributes – the data context and entity types can now be sealed or abstract as well as public, private, protected, internal or protected internal.
- Associations – prevents foreign key values changing once the object association is made and updates parent side of one-to-many associations.
- Stored procedures – generates method wrappers and associated methods to facilitate insert/update/delete with concurrency support.
Functionality compared to designer
A primary goal in developing the template was to allow for easy switching between the template and the LINQ to SQL designer so things are very similar.
Missing
- Comprehensive sanity checking on the DBML.
- The Custom Tool Namespace and project namespaces are not pulled in when the DBML namespaces not specified.
Fixed
The designer has a few bugs which helpfully this template doesn’t suffer from.
- Modifying a table via a stored procedure using original values for concurrency will throw ChangeConflictException and not silently fail.
- Protected internal virtual property doesn’t forget to be virtual.
- Checks all associations based on a foreign key are not loaded before allowing change and not just the first one.
Improved
- Fully customizable with full source.
- Serialization mode to support DataContract improvements in .NET 3.5 SP1
To use uncomment the line // data.Serialization = SerializationMode.DataContractSP1; in xDataClasses.tt
- CanBeNull attribute generated for value types (useful when working with metadata).
Source compared to designer
The designer generated code can be difficult to read and isn’t well suited to template generation so the output from this template is different in a number of ways:
Sequence
Everything related to a column mapping – the storage variable, event signatures, attribute and the property itself – is batched together so it can be hit with a single loop making the template shorter and easier to work with.
#regions
Opinion may be divided on the usefulness of #regions in your own code but for code generation of large files I found it invaluable. There are regions for the logical parts of the data context and within each entity such as construction, column mapping, associations and serialization.
Style
The code generated should be a little easier to follow – if/else ordering, no redundant casts or extra brackets etc.
Namespace
I don’t believe adding “this” everywhere or fully qualifying attributes and exceptions makes things easy to read. I realize this might cause some name conflicts for some people but it is easy to change yourself and means the code is shorter and easier to work with for the majority.
Getting started
Although I work on the LINQ to SQL team this template should be treated as a third-party sample and is not supported by Microsoft.
Download LINQ to SQL for T4 v0.79 (13 KB)
- Add the L2ST4.ttinclude and either CSharpDataContext.tt or VBNetDataContext.tt to your project depending on your language type
- Rename the xDataContext.tt to match your DBML file but with .tt extension instead of .dbml
- Set the existing DBML file's .designer.cs/vb Build Action property to None to ignore the LINQ to SQL built-in code generation
Note that the template will only regenerate when it has been changed so use Run Custom Tool from the template's right-mouse button menu in Solution Explorer when you’ve changed the DBML.
Should you wish to switch back to using the designer code then set the DBML file's .designer.cs/vb Build Action to Compile and either remove the .tt and .ttinclude file for permanent removal or just set the .generated.cs/vb Build Action to None to keep it around. VB.NET users will need to use Show All Files to see the .designer.vb file.
Customization
The template runtime built into Visual Studio 2008 is called T4 and requires no additional tools however if you do a lot of editing you might want to install the Clarius T4 Editor for syntax highlighting and also check out the treasure trove of T4 material that is Oleg Sych’s blog.
The template is simple to follow, it loads the DBML file as an XML document then uses LINQ to XML to instantiate wrapper objects over the elements. This gives you a simple way to change default naming and behavior while making the template simpler to work with.
Let me know how you get on by leaving a comment here.
[)amien
