Over the last 10 years, I've been maintaining several .NET open-source projects, of which one, Fluent Assertions, has been very successful. This year, it crossed the 20 million downloads on NuGet. This may sound like a trivial thing, but I can tell you first hand that maintaining a successful open-source project requires patience, perseverance and a lot of private time. In this talk, I'll share a bit of history about this project. I'll talk about the challenges I've faced around .NET framework compatibility, release strategies and preventing breaking changes. But I will also talk about the dilemma on how to be open to contributions without jeopardizing on the quality of the project. And what about documentation, marketing and how to say no to the community sometimes? Are you also embarking on a new open-source project, or struggling with an existing one? Or do you just want to hear about real-world software challenges? Join me in this little trip through memory lane.

1. Dennis Doomen | @ddoomen | Aviva Solutions | The Continuous Improver

5. var numbers = new[] { 1, 2, 3 };
numbers.Should().Contain(item => item > 2, "at least 1 item should be larger than 3");
action.Should().Throw<InvalidOperationException>()
.WithInnerException<ArgumentException>()
.WithMessage("whatever");
typeof(MyController).Methods()
.ThatDoNotReturn<ActionResult>()
.ThatAreNotDecoratedWith<HttpPostAttribute>()
.Should().NotBeVirtual().And.NotBeAsync().And.NotReturnVoid();
graph.Should().BeEquivalentTo(new
{
RelevantProperty = “ImportantValue”
});

9. “Custom Assertions”
.bat build file
MSTest
CodeBetter TeamCity
2009
CodePlex with TFS
2010
Linked files with #ifdef
First version on NuGet
1.3 (.NET 3.5, 4.0, SL4)
2011
1.7 (.NET 3.5, 4.0, SL4)
CodePlex with Git
2012 (H1)
2.0 (.NET 3.5, 4.0, 3.5, SL4,
SL for WP7.5, WinRT 4.5)
2012 (H2)
Github with Pull Requests
2013
3.0 (.NET 4.0, 4.5, SL5,
Win8, WP8, MonoTouch,
MonoAndroid,)
Psake
David Fowler structure
Shared Projects (.shproj).
2014

10. 3.5 (.NET 4.0, 4.5, Mono, Win
8.0/8.1, WP8 for SL, WP 8/8.1
Store, Sl5)
AppVeyor
GitVersion
2015 H1
4.0 (dotnet5, Mono, Xamarin, .NET
4.0, 4.5, SL5, WP8 SL, WP 8.0/8.1,
Win 8.0/8.1)
PCL + framework-specific +
shared project
Package.json
2015 H2
Cake
xUnit.NET
4.19 (.NET 4.0, 4.5, .Standard 1.3,
Profiel328, Profile32, SL5, UAP
10, WIN81, WP8, WPA8.1)
2017
5.0 (.NET 4.5, Standard 1.4, 1.6,
2.0)
Cross-compilation + #ifdef
PackageReference
2018
Nuke
5.9 (.NET 4.5, 4.7, Core 2.0,
Standard 1.3, 1.6, 2.0)
2019
6.0 (.NET Standard 2.0, 2.1).
2020

11. develop
4.1.0
dogfooding
release-5.0
5.0.04.2.0
5.0.0-rc.1
X
5.0.0-rc.2
master
5.1.0
X
breaking changes
enhancements & fixes
GitHubFlow
GitFlow
SemVer.

13. HTTPS via
CloudFare.
Logo by Ben
Palmer
Github Pages +
Jekyll
Minimal
Mistakes Jekyll
Theme
DNS via
GoDaddy

24. • .NET Standard https://docs.microsoft.com/en-us/dotnet/standard/net-
standard
• David Fowler’s project structure
https://gist.github.com/davidfowl/ed7564297c61fe9ab814
• .NET long-term support
https://dotnet.microsoft.com/platform/support/policy/dotnet-core
• .NET 5 https://devblogs.microsoft.com/dotnet/introducing-net-5/
• Overload resolution bug
https://github.com/fluentassertions/fluentassertions/issues/964
• .NET Core 3 Preview 7 bug
https://github.com/fluentassertions/fluentassertions/issues/1047