Directory.Build.props: C# 9 for all your projects

.NET Core can make use of C9 by making some changes to your .csproj files. There is a way to opt all projects in a solution into this behaviour in a single place, through using a Directory.Build.props file and / or a Directory.Build.targets file. Here's how to do it.

"have you the good news about Directory.Build.props"?

I wrote recently about using C9 with in-process Azure Functions. What that amounted to, was using C9 with .NET Core.

One of the best things about blogging, is all that you get to learn along the way. After I put up that post, Daniel Earwicker was kind enough to send this message:

I was intrigued that Daniel was able to configure all the projects in a solution to use the same approach using some strange incantations named Directory.Build.props and Directory.Build.targets. Microsoft describes them thusly:

Prior to MSBuild version 15, if you wanted to provide a new, custom property to projects in your solution, you had to manually add a reference to that property to every project file in the solution. Or, you had to define the property in a .props file and then explicitly import the .props file in every project in the solution, among other things.

However, now you can add a new property to every project in one step by defining it in a single file called Directory.Build.props in the root folder that contains your source.

Let's see if we can put it to use.

Directory.Build.props: C9 for all

So, rather than us updating each of our .csproj files, we should be able to create a Directory.Build.props file to sit alongside our .sln file in the root of our source code. We'll add this into the file:

Now we're free to add projects into the solution, which will already support C9 without us taking any further steps. It's as simple as that! Thanks to Daniel for sharing this super handy tip. ❤️🌻