Why does LinqPad create Fields instead of Properties?

Question

I recently took on a project of creating a tool for LinqPad that would Dump query results into CSV format in order to use the tool on massive databases for quick results. One thing I wanted out of the tool is for it to be able to work in Visual Studio, and LinqPad. Thus, if I was using LinqtoSQL in VS2010, or LinqPad, I could dump results quickly to a csv file, and then open it up into Excel to view the results.

The biggest hiccup in the project came from how LinqPad builds their DataContexts vs. how Visual Studio builds their DataContexts. The best information I could find on how LinqPad does it comes from here. Basically what I found from my project, was that VS2010 creates properties for their DataContexts, but LinqPad creates Fields. Thus when using reflection:

LinqPad:

dataContextType.GetProperties() //returns 0
dataContextType.GetFields() //returns the Fields from LinqPad created DataContext

VS 2010 LinqToSQL:

dataContextType.GetProperties() //returns the Properties from VS created DataContext
dataContextType.GetFields() //returns 0

So why does LinqPad use Fields instead of Properties in their DataContexts? Wouldn't it have been more feasible to copy the Visual Studio LinqToSQL pattern?

Update

Based on a comment I decided to ask the same question within the LinqPad forum as well.

Answer 1

This is a good question. The main reason for LINQPad using fields to map columns is for performance when building the typed DataContext that backs database-connected queries.

We're not talking about the speed of executing the properties themselves (there's actually very little overhead in executing simple accessors and the JIT may even inline them.) The overhead is when building the typed DataContext via Reflection.Emit. A field is simply that: one item of metadata, whereas a property requires emitting a field definition, a property definition, two methods for the accessors (each with IL to get/set the underlying field). Because users may point LINQPad to databases with upwards of 1000 tables and functions, this can add up in terms of the time taken to build the assembly - as well as its size (increasing HDD activity and working set).

You have raised an interesting issue in the lack of unification between PropertyInfo and FieldInfo in the reflection object model. It would be nice if there was an interface that unified fields and (non-indexed) properties.