Тема: csharp
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Соглашения внедрения зависимостей в .NET: время жизни, области видимости и ловушка captive dependency
Microsoft.Extensions.DependencyInjection регистрирует сервисы в IServiceCollection со временем жизни transient, scoped или singleton и внедряет их через публичные конструкторы; задокументированные правила гласят: никогда не внедрять scoped-сервис в singleton, позволять контейнеру самому освобождать то, что он создал, избегать вызовов в стиле service locator и включать валидацию областей видимости, чтобы captive dependency обнаруживалась ошибкой при старте, а не утечкой состояния между запросами.
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Writing a unit test in JUnit 5 and xUnit.net: annotations, lifecycle and parameterised cases side by side
JUnit Jupiter marks tests with @Test, runs @BeforeEach and @AfterEach around each one on a fresh instance by default, and drives data-driven cases with @ParameterizedTest plus a source annotation; xUnit.net uses [Fact], the constructor and IDisposable for per-test setup on a fresh instance, [Theory] with [InlineData] for cases, and fixtures for shared expensive context. Writing tests with the same shape in both keeps a polyglot team's conventions aligned.
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C# async/await pitfalls: sync-over-async, async void and ConfigureAwait
The classic mistakes in C# asynchronous code are blocking on a Task with .Result, .Wait() or GetAwaiter().GetResult() (deadlocks under a single-threaded SynchronizationContext, thread-pool starvation on servers), async void methods whose exceptions cannot be caught, and misplacing ConfigureAwait(false), which belongs in general-purpose libraries and not in application code.
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Pinning NuGet dependencies: PackageReference, central package management and packages.lock.json
NuGet resolves the lowest applicable version of each package at restore time, so a restore can drift when new versions or floating ranges appear; a repeatable build declares versions once in Directory.Packages.props, enables RestorePackagesWithLockFile so packages.lock.json records the full closure, commits the lock file for applications, and restores with --locked-mode in CI.
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Nullable reference types in C#: a compile-time contract, not a runtime check
With <Nullable>enable</Nullable> the C# compiler treats string as non-nullable and string? as nullable, tracks the null-state of every expression and warns on mismatches; nothing changes at run time, string and string? are the same type, and the null-forgiving operator ! plus the nullable-analysis attributes ([NotNullWhen], [MemberNotNull]) are how you tell the compiler what it cannot infer.
Машиночитаемо: JSON