Browsing posts in: .net

Using Roslyn and unit tests to enforce coding guidelines and more

Last year, during a few of my Roslyn talks, I was presenting a cool idea of leveraging Roslyn in unit tests to enforce a certain style in code, and in general inspect the consistency of the code in various ways.

It’s a really powerful concept, and something I wanted to blog about, but of course forgot – until I was reminded of that yesterday on Twitter.

Let’s have a look.

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Running a C# REPL in a DNX application with scriptcs

One of the cool things that scriptcs allows you to do, is that you can embed it into your application and allow execution of C# scripts. There are even some great resources on that out there, like this awesome post by Mads.

The same applies to the REPL functionality – you don’t have to use scriptcs.exe to access the REPL – you can use the scriptcs Nuget packages to create a REPL inside your app.

And because there aren’t that many resources (if any) on how to host a scriptcs REPL, today I wanted to show you just that. But for a more interesting twist, we’ll do that inside a DNX application.

There are many reasons why DNX is awesome, and why you’d want to use it, but especially because, through the project.json project system, it has a much improved way of referencing and loading dependencies and Nuget packages – and we can leverage that mechanism to feed assemblies into our REPL.

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Hacking DNX to run C# scripts

Because of my considerable community involvement in promoting C# scripting (i.e. here or here), I thought the other day, why not attempt to run C# scripts using DNX?

While out of the box, DNX only compiles proper, traditional C# only, thanks to the compilation hooks it exposes, it is possible to intercept the compilation object prior to it being actually emitted, which allows you to do just about anything – including run C# scripts.

Let’s explore more.

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Disposing resources at the end of Web API request

Sometimes you have resources in your code that are implementing IDisposable, and that you’d like them to be disposed only at the end of the HTTP request. I have seen a solution to this problem rolled out by hand in a few code bases in the past – but in fact this feature is already built into Web API, which I don’t think a lot of people are aware of.

Let’s have a quick look.

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Action filters, service filters and type filters in ASP.NET 5 and MVC 6

Today, let's have a look at he area of filters in ASP.NET MVC 6 – because it actually contains quite a few interesting changes compared to classic MVC and Web API filter pipelines.

Let's leave the specialized filters (error filters, authorization filters) on a side for now, and focus instead on the functional, aspect oriented, filters. Aside from the good old action filters, known from both MVC and from Web API, there are two new types of filters (or rather filter factories, but we’ll get there) that you can use – ServiceFilters and TypeFilters.

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Integration testing ASP.NET 5 and ASP.NET MVC 6 applications

The other day I ran into a post by Alex Zeitler, who blogged about integration testing of ASP.NET MVC 6 controllers. Alex has done some great work for the Web API community in the past and I always enjoy his posts.

In this case, Alex suggested using self hosting for that, so spinning up a server and hitting it over HTTP and then shutting down, as part of each test case. Some people have done that in the past with Web API too, but is not an approach I agree with when doing integration testing. If you follow this blog you might have seen my post about testing OWIN apps and Web API apps in memory already.

My main issue with the self-host approach, is that you and up testing the underlying operating system networking stack, the so-called “wire” which is not necessarily something you want to test – given that it will be different anyway in production (especially if you intend to run on IIS). On the other hand, you want to be able to run end-to-end tests quickly anywhere – developer’s machine, integration server or any other place that it might be necessary, and doing it entirely in memory is a great approach.

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How ASP.NET MVC 6 discovers controllers?

In the past I did a couple of blog posts (here and here) about how ASP.NET Web API discovers controllers.

ASP.NET MVC 6 supports both regular controllers (inheriting from Controller base type) and POCO controllers. Let’s have a look at how the discovery of them happens in ASP.NET MVC 6. Note that the code and mechanisms discussed in this article were introduced after ASP.NET 5 beta3 was released, so it is not yet available if you use the version of ASP.NET 5 bundled with Visual Studio 2015 CTP6.

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Strongly typed routing for ASP.NET MVC 6 with IApplicationModelConvention

This is something I hacked together last night, but it was a very interesting exercise into customizing the new (or rather, future) ASP.NET MVC 6 to suit your needs.

If you visit this blog from time to time, some time ago I blogged about building strongly typed routing provider for ASP.NET Web API (code is here). That was built around extensibility points provided by the direct routing mechanism (better known as direct routing’s default implementation – attribute routing).

So I thought, it would be fun to port this solution to MVC 6. However, while MVC 6 supports attribute routing, it does not provide the same abstractions over the routing mechanism. Instead it exposes something new for both MVC and Web API developers – IApplicationModelConvention, which is what we’ll use here.

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Migrating from ASP.NET Web API to MVC 6 – exploring Web API Compatibility Shim

Migrating an MVC 5 project to ASP.NET 5 and MVC 6 is a big challenge given that both of the latter are complete rewrites of their predecessors. As a result, even if on the surface things seem similar (we have controllers, filters, actions etc), as you go deeper under the hood you realize that most, if not all, of your pipeline customizations will be incompatible with the new framework.

This pain is even more amplified if you try to migrate Web API 2 project to MVC 6 – because Web API had a bunch of its own unique concepts and specialized classes, all of which only complicate the migration attempts.

ASP.NET team provides an extra convention set on top of MVC 6, called “Web API Compatibility Shim”, which can be enabled make the process of migration from Web API 2 a bit easier. Let’s explore what’s in there.

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ASP.NET MVC 6 attribute routing – the [controller] and [action] tokens

When working with attribute routing in Web API 2 or MVC 5 it was relatively easy to get the route to the controller and the controller name out of sync. That was because the route always had to be specified as a string, so whenever you changed the name of the controller you would always have to change the string in the route attribute too.

That could be easily forgotten – especially if you use refactoring tools of Visual Studio or an external refactoring plugin.

This issue has been addressed in MVC6 with a tiny addition – the introduction of [controller] ad [action] tokens into attribute routing.

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