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Tag: async

23 posts · Page 2 of 3

2026-06-20 csharp dotnet async

What is ValueTask<T> and when is it worth it?

ValueTask and ValueTask<T> are structs that let an async method return a result without heap-allocating a Task when it completes synchronously. The win is one fewer allocation on hot paths that usually finish without awaiting. The cost is a strict await-once contract. Here is what the type actually is, how it works, and the narrow set of cases where it earns its keep.

2026-06-19 csharp dotnet dotnet-11

What is IAsyncEnumerable<T> and when should I use it?

IAsyncEnumerable<T> is the interface for asynchronous streams: a sequence whose elements arrive over time and each one may require an await. Here is what it actually is, how await foreach and yield drive it, and the rule for when to reach for it over Task<List<T>>.

2026-06-06 migration csharp dotnet

Migrate from ValueTask<T> back to Task<T>: when and why (.NET 11, C# 14)

A practical checklist for reverting ValueTask and ValueTask<T> return types to Task and Task<T>, what breaks at the call sites, how to verify each change, and how to know whether the swap was ever worth it.

2026-06-02 errors csharp dotnet

Fix: ObjectDisposedException: Cannot access a disposed context instance

Your fire-and-forget task captured a request-scoped DbContext that the DI scope already disposed. Resolve a fresh context inside the task with IServiceScopeFactory or IDbContextFactory.

2026-05-31 csharp dotnet dotnet-11

How to run fire-and-forget work safely in ASP.NET Core with BackgroundService

Calling Task.Run from a controller loses work on shutdown, swallows exceptions, and captures disposed scoped services. The safe pattern is a bounded Channel queue drained by a BackgroundService that opens a fresh scope per work item and drains in-flight work on StopAsync.

2026-05-25 comparison csharp dotnet

Parallel.ForEach vs Parallel.ForEachAsync vs Task.WhenAll in C#

Use Parallel.ForEach for CPU-bound work over in-memory data, Parallel.ForEachAsync for async I/O over many items with a concurrency cap, and Task.WhenAll for a small fixed fan-out where you want every operation in flight and need the results back.

2026-05-21 comparison csharp async

ConfigureAwait(false) vs default in .NET 11: does it still matter?

ConfigureAwait(false) is still mandatory in library code that may run under a SynchronizationContext (WinForms, WPF, MAUI). In application code on ASP.NET Core, a console app, or a worker service running on .NET 11, it is a no-op.

2026-05-21 comparison csharp linq

IEnumerable vs IAsyncEnumerable vs IQueryable in C#: which one should the method return?

Three sequence interfaces, three execution models. Use IQueryable when a database can translate the query, IAsyncEnumerable when the producer is async and you want to stream, IEnumerable for everything else in memory.

2026-05-20 comparison csharp async

async void vs async Task in C#: when each is correct

async Task is the default and async void is the exception. Use async void only for event handlers, top-level message-loop handlers, and a handful of framework callbacks that demand a void signature. Everywhere else, async Task wins on exceptions, composition, and testability.

2026-05-07 errors csharp dotnet

Fix: A second operation was started on this context instance before a previous operation completed

EF Core throws when two awaits run in parallel on the same DbContext. Await each call sequentially, or get a new DbContext per concurrent unit of work via IDbContextFactory.