C#/.Net Generic constraints

Hi

Despite having no doubt about the usefulness of type constraints in C# generics (this is a key feature to help avoiding bugs when writing generic code in C#) I always had  the impression that it should be able to express more constraints than what the C# language / compiler exposes.

Well, some time ago this blog entry called my attention on my RSS reader and motivated me to go and scan the .Net specification (more specifically § II.10.1.7 in the CLI Metadata Definition and Semantics document which can be downloaded from here) and to my surprise I found out that in addition to the valid C# generic constraints CLI also support constraining a generic argument to delegates, arrays and even enums! That is nice.

Next question is: does the C# compiler abides by these rules when consuming assemblies?

To answer this question I wrote a small class library (in C#) that exposes some generic types and manually (ildasm/ilasm) added each of these constraints. After that I created one application (C#) that uses this library and confirmed that C# compiler does respect these constraints (at least in VS 2010 which uses CSC 4.0.30319.1). Bellow you can see the result of trying to use these generic types with incompatible types:

Generic parameter 'E' was constrained to enums

Generic parameter 'A' was constrained to arrays. 

You can download the sample application from here.

The bottom line:  Generic constrains in .Net  are more useful than what you may be lead to believe ;)

As always, don't be shy! Let me know what you think.

Hope you find this useful.

Windows 8 / Visual Studio 2012

Hi

Getting back to the subject I am more comfortable with, MS just released Windows 8 / VS 2012 (for MSDN and Technet subscribers). Off course I am downloading both right now but this is the first time, since Windows 95 launch, that I am not going to install the new MS OS as soon as it gets released. 

To be honest I am not even considering installing it (on my main dev machine) in the next 6 ~ 12 months! Contrast that to what I've been doing in the past (I've used Vista / Windows 7 RC!) and you can see how "excited" I am about it (maybe I install it on a virtual machine so I can experiment with it). Anyway, sooner or later I'll end up formatting my dev machine and the question is: am I going to give Windows 8 a try? Or shall I take a more drastic approach and install Ubuntu? This bring me to the second MS release.. VS 2012.

One of the main reasons I'm procrastinating migrating to a Linux OS is that I really enjoy developing using .Net (yeah, I do know Mono; the problem is: the bulk of .Net development is still concentrated on MS platform. Also, IMHO, *nix lacks a good .Net IDE).

Of course my friends (at least the ones in the software development field) knows that that is not completely  true: I also enjoy MS technology in general (COM+ pops up as one example).

What do you think? Should I dive into Windows 8?

BTW: Visual Studio download finished! This one for sure I'll get installed in the next few days ;)

Happy codding!

Db4o with Visual Studio 10 / .Net Framework 4

Hi.

When Microsoft announced they would make available VS 2010 CTP I got curious about how easy (or hard) it would be to compile / run Db4o and also how OMN would behave in this early CTP (would it just work, without even require a recompilation? If not, how easy/hard it would be to make it work if possible at all, etc).


Well, yesterday I managed to download the CTP; after extracting the files (24 Gb!!) I just took OMN 2008 installation and give it a try. It was really amazing. The only change I've applied was to update the file %ALLUSERSPROFILE%\Application Data\Microsoft\MSEnvShared\Addins\OMAddin.addin in order to change the target VS (OMN 2008 will set it to 9.0 but VS 2010 is 10.0). 


After this change I just fired up VS and OMN addin was there, working with no issues (as far as I tested :)) as you can see in the screen shot bellow. Cool.

Next step was to load Db4o 2008 solution file; VS 2010 asked whenever I'd like to convert the solution/project files to the newer version; I just consent to that and when it finished converting I just run Db4o Tests. 

This time some tests failed due to missing jars (I didn't run a full build) required to run Java/.Net compatibility tests; besides that expected failure,  only one test failed (I just disabled it for now).


My next steps will be:

1. Try to understand / fix the falling test.
    
2. Prepare the environment to at least run the target "build-before-checkin"  defined in build.xml (and uncomment any test commented out to make the tests pass).
   
   
3. Reason whenever it makes sense to use some of C# 4.0 / .Net Framework 4.0 new features (for instance dynamic types) and how Db4o handle them.
   

Since these will require more time to investigate / test I'll leave them for a forthcoming post.

Adriano

Are you a C# developer?

If so, you should go and grab a copy (for free) of CodeRush Xpress for Visual Studio!

(I already own a copy of another addin, but I'll give it a try anyway :)

Adriano