Dynamic LINQ2SQL to an unmapped table

Question

I'm working with an application which allows customers to create and import custom tables. I have the need to allow those customers to build dynamic queries against the imported custom tables and I would like to be able to use LINQ to do this.

I'm familiar with how to create Dynamic LINQ queries however all the methods I know of require an existing mapped object on the DataContext object. As users are able to create custom tables at runtime (through dynamic string built SQL) there isn't a mapped object in any DataContext.

Is there a way to dynamically create a DataContext and mapped object at runtime for use with a dynamic Linq query?

Is there some other way to do this without resorting to string built sql?

Answer 1

There are some T4 templates available for creation of Linq to SQL data classes. Perhaps you can adapt those.

http://www.pnpguidance.net/Post/LINQToSQLCodeGenerationT4TemplatesTutorials.aspx

There are two ways that I can think of to generate the assembly without requiring the Microsoft C# compiler or Visual Studio. The first is to use System.Reflection.Emit to generate a custom assembly. This might be easier than it sounds; have a look at the following add-in for Reflector:

ReflectionEmitLanguage Add-in for Reflector
http://reflectoraddins.codeplex.com/wikipage?title=ReflectionEmitLanguage&referringTitle=Home

What the add-in does is take an existing IL assembly and create C# code that contains the System.Reflection.Emit calls that it would take to generate the same IL that the C# compiler would. So essentially what you would do is create an assembly containing a prototype DataContext, and run this on its methods. You would then have a class (or the better part of one) that will generate the IL assembly directly. All of this code is open-source.

The other thing you could do is try using the Mono C# compiler (which can be called like a service, unlike the Microsoft C# compiler) to generate your IL assembly. The C# compiler is also open-source.