Category Archives: T4

Entity Framework View Generation Templates Updated for Visual Studio 2015

Entity Framework 7 may be around the corner and when it ships view generation will no longer be a concern because EF7 is not using views to abstract the database anymore. As of now, however, EF7 is still in beta and – as per the schedule – it will take another few months for it to be released. Even when it ships I don’t think many existing applications will ever move to EF7. In fact, there is still a lot of applications using EF5 or even EF4 that were never moved to EF6 and moving a pre-EF7 based app to EF7 may be even more difficult. In the meantime, Visual Studio 2015 was released. And while people not necessarily want to move their apps to use newer versions of dependencies many of them want to move to the latest available tooling. To make it possible I updated all the view generation templates so that they work with VS 2015. So, if you use or plan to use view generation templates in your applications download the latest version(s) from Visual Studio Gallery or install them directly from within Visual Studio. (Note that view generation templates in existing projects will continue to work in Visual Studio 2015 without this update. This update is required if you needed to add a new template to a project).


EF6 CodeFirst View Generation T4 Template for C# updated for EF6 RTM

The story around pre-generated views in pre-release versions of EF6 was far from glorious. First, things did not work in EF6 Beta1 due to this bug. Then the bug was fixed but due to other changes in this area pre-generated views were broken again in EF6 RC1 (mainly because of the combination of this and this). Because of the issues in the EF6 RC1 I decided not to post the version I had – it just did not work. Finally, it turned out that due to changes in the EF Tooling shipping with Visual Studio 2013 the template did not want to work on Visual Studio 2013 (or Visual Studio 2012 where the new tooling is available out-of-band). That’s a pretty interesting story on its own but for me it meant that I basically had to rewrite the template. Today EF6 has finally landed (btw. Visual Studio 2013 shipped today too) Since the bugs around pre-generated views were fixed I updated the EF6 Code First T4 template for generating views and posted the latest version on the Visual Studio Gallery. The template should work on Visual Studio 2010, Visual Studio 2012 and Visual Studio 2013 and for EF6 RTM and nightly builds. If you need steps to install and use the template take a look at this post.
A couple additional notes:
– an updated version of EF Power Tools which allows generating views (and more) directly from Visual Studio version was shipped recently
– view generation in EF6 has been greatly improved so maybe you don’t really need to use pre-generated views?

(Because you read this post you might be interested in this.)

T4 Templates for Generating Views for EF4/EF5 Database/Model First apps

After we received a comment on the EF team blog asking why the templates for generating views for Edmx based apps we posted years ago were not updated for EF5 Rowan asked me if I it would be possible to update the template so that it works for EF5. I actually remember looking at this template before I shipped my templates generating views for Code First apps and one of the first things I noticed was that the way it handled versions was robust but not very flexible. Therefore, when we shipped EF5, the templates could not be used with apps using v3 of the EF artifacts (edmx). I thought a bit more about this when I was working on the templates for CodeFirst and concluded that robustness is not really very important here. If someone wants views they will have to provide a valid model (be it Code First model or Edmx) or the APIs used for generating views will throw an exception. Since the exception will be displayed in the error pane (and should be understandable for any person who is trying to use pre-generated views) there was no need to sacrifice flexibility for robustness. Also, the expierence of using the template was not very good. It was posted as a .zip file attached to a blog post. Not only wasn’t it discoverable but you would also have to take a number of extra steps to be able to use it. Visual Studio Gallery makes it much easier to find and use extensions like this, so I thought it was not a bad idea to revamp the template and ship it on the VS Gallery (especially given that I already have all the infrastructure needed to create a shippable .VSIX files containing a T4 templates). The only thing I was missing was the template itself. Luckily(?) I was investigating a bug which I thought could be worked around by using pre-generated views. After I finished up coding the template it turned out that this is not the case (i.e. you cannot use pre-generated views if you have QueryViews in your mapping) but at least I had a T4 template for generating views for Database/Model First apps. Now I only had to marry the infrastructure for building .vsix with the template and call it done (I went a bit further and even created a VB.Net version of the template). Since yesterday the templates are available on Visual Studio Gallery – the C# version can be found here and the VB.Net version can be found here. Using the templates is simple. In Visual Studio right-click on your project and select Add→New Item (Ctrl+Shift+A). In the “Add New Item” window select “Online” on the left. You may want to filter by EF5 or edmx. Select the “EF4/EF5 Model/Db First View Gen .tt for {C#|VB.Net}”. Change the name of the .tt file so that it starts with the name of your edmx file (i.e. if your edmx file is called “MyModel.edmx” name the template “”) and press the “Add” button:

Add New Item - Edmx Views

Add New Item – Edmx Views

and that’s pretty much it – the template and a class containing views should now be added to your project:
Project with views

Project with views

If you want to enforce re-generating views (e.g. after the edmx file changed) just right click the .tt file and select “Run Custom Tool”.
If you need to uninstall the template go to Tools→Extensions and Updates… select the template from the list and click the “Uninstall” button.

My Late Reflections on T4

Friday the 13th – a perfect day for grumbling. And I mean it – it’s going to be counterproductive and is not going to help you with anything (at most you will be able to say “Me too!” or “I am not alone”). I am going to grumble about probably well known things and a few years too late. So if you are having a good day my advise would be to stop reading now. I typically don’t grumble but just move on but this time I already had the content so it made it easier. All this started with an email from a colleague from my old team looking for someone on the EF team who “owns” T4 templates. I answered that there is no such person since probably more than half people of the team had to deal with the templates so if he had any specific question he could send it to me and I would either answer or add to the thread someone who would be able to answer. It turned out that they had a tool that generates code – a kind of an .exe or something even worse (but not as bad as perl) and were looking at moving to T4 and he asked me what were my thoughts on this. The first thought was that moving to T4 was in general not a bad idea (and I still think it is given what they currently have). However when I started gathering “my thoughts” I concluded that every rose (even a dead one – pun intended) has its thorn.

  1. Out of the box a T4 template can spit just one file. This sucks a big time – you can end up having a file with hundreds of classes. There are some ways of working this around but they usually make your template cryptic and messy (as if it was already not the case) since all the logic has to live in the template itself
  2. Visual Studio does not have a built-in editor for T4. This makes it even harder to see what’s going on in the template (as if it was not hard enough). There are 3rd party tools/add-ons that provide syntax coloring and perhaps intellisense. I have not tried any them otherwise I could have one less thing to grumble about
  3. Developing T4 templates is messy. At first it feels a little bit like classic ASP. After a while you start adding some functions and soon the code looks pretty much like a classic ASP page which – when you scroll down – gradually turns into a kind of procedural code like C or Pascal. You could try using ttinclude but it does not help a lot – now ‘ASP’ is in one file and ‘Pascal’ in the other file
  4. If you have to ship templates generating code for both C# and VB.NET you most likely won’t be able to re-use most of the logic which means you have to replicate the code (as if shipping VB.NET version was not painful enough)
  5. T4 templates are basically not testable. To be able to write some kind of unit tests you would probably have to create a custom transformation host for testing. The problem is that even if you did that it does not solve the problem since T4 transformations can behave differently for different hosts so you would not be testing the thing the way it will eventually be used/executed anyways
  6. You supposedly can debug T4 templates. Realistically you can forget about it. For me it is like Santa – I know he exists but have never seen him. Maybe it works for very simple templates but once you start doing more complicated things it will just not work (never worked for me at least) and you will end up using “WriteLine” debugging – welcome to the nineteen-eighties
  7. If you screw something up, in the best case you will get an exception displayed in the error pane which – if you find the correct stack frame – sometimes can be even helpful. Otherwise you will just get a message saying “Error Generating Output” in your output file – and then you need to debug (see above)
  8. Some more advanced things may be impossible – I recently tried to spin a new AppDomain to run some code I could not run inside the transformation app domain (have you seen how my view gen templates break when you install new EF Designer? – I wanted to fix that by using a separate app domain) and had to give it up. Could not make it work since I did not have enough control over generating the class that included my transformation code, nor how the transformation is being run
  9. People are afraid of T4 and don’t realize that they can actually modify the template they added to the project and it will not break their Visual Studio. I think this is because of what they see when they open a T4 template first time (did I mention it looks messy and cryptic – especially if you don’t have syntax coloring?)
  10. It’s nice that you can ship T4 templates as vsix packages but Visual Studio is not really helpful in preparing those – at least I had to prepare the EF view gen templates mostly manually. I have been wanting to describe steps for shipping T4 templates as vsix files for a while but so far have not managed to

This is just grumbling – the T4 technology has been around for a while and my grumbling is not going to change anything there. I also don’t think there is anything better for text transformations that ships with Visual Studio so, as my mom would say, “if you can’t have what you like you have to like what you have”. Tomorrow will be a better day 🙂

EF Designer now supports EF6

Some time ago I showed how to hack the EF Designer shipped with Visual Studio 2012 to work with EF6. Those hacks should be no longer needed – last week we shipped Entity Framework 6 Beta1 which for the first time contains not only EF6 runtime but also contains tooling. The new EF Designer works with Visual Studio 2012 and replaces the designer that was originally shipped with Visual Studio 2012. Almost all the work we did was about adding support for EF6 – being able to handle new metadata types, using the new provider model, creating EF6 specific T4 templates etc. This work has not been completed yet and some scenarios like support for EF6 on .NET Framework 4 or using non-SqlServer (or SqlServerCE) providers when using EF6 are still not enabled but if you want to use model first/database first workflows with EF6 the Beta version is currently your best option. Note that even though this release is mostly about adding support for EF6 we are not abandoning EF5. For EF5 the EF Designer Beta 1 version supports all the scenarios that were supported by the previous versions. You choose the target version of Entity Framework in the wizard when adding a new model to your project (note that in some cases the choice is limited – e.g. if your project already has a reference to System.Data.Entity.dll you won’t be able to select EF6).

It’s not a June CTP kind of thing
EF6 runtime is no longer shipped as part of the .NET Framework and we did not have to do hacks we had to do when shipping tooling in June 2011 CTP. It means that it is easy to install the EF Designer Beta 1 but it is also easy to uninstall it and go back to the original designer shipped with Visual Studio 2012 – just go to Programs and Features, uninstall the new designer and repair Visual Studio and things should work as they did before.

How to get it?
Just go to the download center and install the msi.

We want your feedback
Since the new EF Designer is easy to install and uninstall and it supports all the scenarios supported by the old one I would like to encourage everyone to try it out and let us know about your experience (and issues). This is only a Beta version and we already know it has some rough edges but it may also have bugs we don’t not know about yet. Try it out and if you see something start a new discussion or create a new work item.