async and await are not runtime features up to .NET 10. They are a compiler rewrite. When you mark a method async, the C# compiler removes the method body, moves it into a generated type, and replaces the original method with a few lines that create and start that type. Everything else, the scheduling, the exception handling, the value that eventually lands in the returned Task, is ordinary code you could… [read more]

Ask most C# developers what you can await and the answer is "a Task". That is the common case, but it is not the rule. await is resolved the same way foreach is: structurally. The compiler looks for a shape, and Task happens to have it. Knowing the shape is what makes the next post, on the generated state machine, readable. It also lets you write awaitables of your own, which is occasionally very useful.… [read more]

So far this series has looked at threads and at the operating system. This post is about the object in the middle: Task. It predates async/await by a release, and understanding it separately makes the compiler rewrite in the next posts much easier to read. A Task is a promise of a future result. It is not a thread, not an operation, and not a unit of work. It holds three things: a state, a result or an… [read more]

The previous post showed that blocking a thread while waiting for I/O throttles everything else the process wants to do, and that awaiting instead does not. That raises an obvious question: if no thread is waiting, who is waiting? The answer is that nobody is. There is no thread. This post is about what that actually means, because it is not a figure of speech. Proving it first The sample starts 100 000… [read more]

This is the first post of a series about async/await in C#. Before looking at how it works, it is worth being precise about what problem it solves, because the usual explanations are either vague ("it makes your app faster") or wrong ("it runs your code in the background"). async/await does not make anything faster. A network call takes as long as it takes. What it changes is what your process does while… [read more]

In , we used JsonNode as the input type. If your data is already loaded in domain classes, you can evaluate JsonPath directly on those classes without converting to JsonNode. Meziantou.Framework.JsonPath exposes JsonPathNavigator<TValue> for this scenario. You provide JSON-like navigation semantics for your node type, and the evaluator does the rest. This is the same approach as in , where we exposed… [read more]

When you need to extract values from complex JSON payloads, manual navigation quickly becomes hard to read and maintain. Meziantou.Framework.JsonPath provides a JSONPath implementation for System.Text.Json based on RFC 9535, so you can query JSON documents using concise, standard expressions. Installation Install the package from NuGet: dotnet add package Meziantou.Framework.JsonPath Parse and evaluate a… [read more]

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]