In , I showed that XPathNavigator is not tied to XML. Any tree can be exposed as a node-set, and the XPath engine of System.Xml.XPath does the rest. That post used a folder hierarchy as an example. Here is a much more interesting tree: the C# syntax tree produced by Roslyn. The occasion for it was an issue on Meziantou.Analyzer: Rule to forbid primary constructors? (Opposite of IDE0290). The request was… [read more]

XPath is widely known as the query language for XML documents. Most .NET developers associate it with XPathNavigator, XmlDocument, or XDocument. But what most people don't realize is that XPath can work with custom types too. In this post, I'll show you how to implement XPath for your own types and how it can be useful for searching complex object hierarchies. The problem Imagine you have a rich object… [read more]

Choosing a test framework in .NET used to be a question of taste. xUnit, NUnit, and MSTest all discovered tests by reflection, all ran on VSTest, and the differences that mattered were the attribute names and the assertion style. Performance was not part of the conversation because there was nothing much to compare. Two things changed that. Every framework now ships a Microsoft.Testing.Platform runner,… [read more]

Integration tests are much more valuable when they run against real services. Instead of mocking a database or cache, you can start a temporary container, run your test, and dispose everything at the end. The Meziantou.Framework.TemporaryContainers package provides a lightweight API to manage disposable containers from .NET. Its main difference with the existing libraries is that it is not tied to Docker.… [read more]

When maintaining a library, one of the easiest ways to introduce a breaking change is to update a public type without noticing its impact on consumers. You can use the Microsoft.CodeAnalysis.PublicApiAnalyzers analyzer to generate a file with the list of members. However, I don't like it as the members are not in C# syntax. Also, if you don't have the same public API for all target frameworks, you get… [read more]

When you add a NuGet package to a project, you often think about the runtime library only. In reality, packages can also import MSBuild props/targets and Roslyn analyzers. Those assets run during restore, design-time build, or build. I've already provided some examples of how this can cause issues in . This means a package can execute code on your machine or in CI without you notice. If you only need a… [read more]

Reproducible builds in .NET replace file paths with placeholder values to enable reproducible builds and prevent leaking local development paths in binary outputs. This is a common practice on CI/CD pipelines. However, libraries that rely on actual file paths to function, like snapshot testing frameworks, face a challenge: they need to know where to store and load snapshot files on disk. This post… [read more]

Snapshot testing is a technique where the output of a function or component is serialized and saved to disk the first time the test runs. On every subsequent run, the library re-serializes the output and compares it against the saved file. If they differ, the test fails. Meziantou.Framework.SnapshotTesting is a .NET library that makes snapshot testing straightforward. It handles serialization, file… [read more]

Adding a Clone method to a C# record When using records, creating a copy with with is concise: var sample = new Sample("meziantou"); _ = sample with { }; public record Sample(string Value); This works well, but sample with { } is not always obvious as a discoverable Clone API for consumers. Why public Sample Clone() is not allowed Records already have compiler-generated clone behavior used by with.… [read more]

If you have a Rune and want its Unicode name (for example GRINNING FACE for 😀), there is no built-in API in .NET today. Here are two practical options: Use the ICU library available on the operating system Use the Meziantou.Framework.Unicode NuGet package Method 1: Use ICU from the OS ICU exposes u_charName, which returns the Unicode name for a code point. using System; using… [read more]