IAsyncEnumerable Explained — Async Streams in .NET

IAsyncEnumerable, yield return, cancellation tokens, vs IEnumerable, real-world streaming Most developers know IEnumerable<T> and async/await . IEnumerable<T> — lets you iterate a sequence. async / await — lets you do I/O without blocking threads. But IAsyncEnumerable<T> — introduced in C# 8 — combines both, and it solves a problem that neither alone handles well. It lets you iterate a sequence asynchronously — yielding items one at a time as they become available, without loading everything into memory first. The Problem They Solve Imagine reading 100,000 records from a database and returning them to the caller. Option 1: Return everything at once public async Task < List < Order >> GetAllOrdersAsync () { return await db . Orders . ToListAsync (); // ❌ Loads everything into memory } Memory spikes. The caller waits for the entire load. Option 2: Synchronous yield public IEnumerable < Order > GetAllOrders () { foreach ( var order in db . Orders ) // ❌ Blocks the thread yield return orde