T4 Templates don't work in asp.net core

[Guy--L]

I've tried to adjust things but have not had any success with asp.net core, vs2017 rc3.

Is there a plan?

[pleb]

I would love to port PetaPoco to .net core, and hopefully one day I will, however, it comes down to time.

In the .net core world, the T4 schema generation would be replaced with the a new tool which would be added to the tools section of the project file. See tools

[Guy--L]

I see some posts at large regarding code generation for .net core. It sounds like you have a clear idea of your approach given the time. I have some time if you're willing to outline the approach.

[6pac]

Any updates on this? I've just set up a new PetaPoco project in Net Core 2, and it was pretty easy to get it working. Seems like a lot of the stuff that was prompting a rework in Core 1 has been re-added in 2.

In PetaPoco.cs (approx line 205) and PetaPoco.Core.ttinclude (approx line 349), replace:

_factory = DbProviderFactories.GetFactory(_providerName);

with:

_factory = System.Data.SqlClient.SqlClientFactory.Instance; // DbProviderFactories.GetFactory(_providerName);

Ensure System.Configuration.ConfigurationManager, System.Data.Common, System.Data.SqlClient (in my case) are installed with NuGet, and you should be able to build.

I am also getting an ugly error when building the T4 templates in VS2017. It appears that these are officially supported in VS2017, but it's choking with a SerializationException in GetCurrentProject(), on the line

EnvDTE.Project dteProject = (EnvDTE.Project)activeSolutionProjects.GetValue(0);

I can still build the T4 template if I right click and choose the 'debug T4 Template' option - that seems to work. And at times the regular build fixes itself for a while, but then later starts throwing this exception again. Pretty flaky.

Just wondering two things:

• if we're moving away from T4 Templates, what's a good alternative? I can't find anything for design time scripting that's able to be project and db aware, without essentially rewriting the T4 function from the ground up
• it appears PetaPoco is mainly downloaded by NuGet these days, and say AsyncPoco is dropping T4 support altogether. Does that mean that people are hand writing the templates? Are people really not using autogeneration? This is at the core of the tool for me.

[Guy--L]

I have T4 working in vs2017 modified for NPoco two weeks ago. I notice the same error on the first save. But usually after the second save, it generates my pocos each time. Scripty is a tool I was considering--to replace T4 files with csx script. But now that's moot.

[6pac]

Yeah I don't think Scripty can do the database access in the same way, or at least not without a lot of gymnastics. The T4 templates are surprisingly flexible.

[hippasus]

hi, do you want to try this tool PetaPoco.DBEntityGenerator I just built? I've ported the T4 template into this tool. It supports net core.

[6pac]

I note I have found a fairly simple mod that fixes the T4 generation, I've been doing it happily for some months now. It's a bit of a hack, I have been waiting to find the time to review it and make something more graceful.

[picasso566]

@hippasus Trying out your generator tool and looks good. I was going to start from scratch and maybe use something like
https://github.com/iQuarc/Geco I like how it uses string interpolation on .cs templates. You are in essence doing almost the same thing.
@6pac I am also looking for a solution that will work outside of Visual Studio (moving towards VS Code) so the T4 templates are unfortunately not going to work. I have used them for years and grown to depend on them, it's too bad.

[6pac]

@picasso566 Yeah, I have been using the T4 templates since SubSonic 3, but frankly I have to say they suck. They are fine if nothing changes and you leave them alone, but if you change them they are extraordinarily hard to debug if there are any problems (I end up applying changes a few lines at a time, because otherwise it's impossible to work out what broke and why).
Add to that the problems compiling them in later versions of VS, and it doesn't add up to a happy customer.
However I have modified the original templates substantially, and I am not keen to spend the time converting them all to some new format unless it is going to be well supported into the future.

[6pac]

@hippasus I'll have a look at your tool, I'm leaning towards an open source solution so I have some assurance of long term viability.

[picasso566]

All I know is, one of the big draws for me to PetaPoco (for the last 10 years in my case) was the auto generated classes and decorators in the T4 templates. One of the reasons I've been using Petapoco over Dapper or something else. They really speed things up for me.

[pleb]

I know people love the class generation T4 stuff. I'd like to have a good solution here, but it's not the easiest thing to solve without a fair bit of time and effort. Although I haven't used it yet, the generator from @hippasus looks awesome and seems to support all the major DBs, so it gets my vote.

[pleb]

If you're using netcore, don't forget EF can reverse eningeer now too. I don't mind EF Core (>= 3.1) and it's much better than EF 6. If you configure it correctly, you can get some good preformance out of it.

[iadaz]

Another approach I've had success with is using the "LoadTables()" function from the old version, and pushing the result of that through templates created in Razor syntax, using https://github.com/Antaris/RazorEngine. Unfortunately RazorEngine doesn't have a maintainer so is stuck in full .net framework. Razor has some quirks when used outside of its natural environment, but will at least offer up intellisense for most things.