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.NET Full Stack

Async & Concurrency Essentials

Async execution, Task composition, cancellation, blocking hazards, shared-state safety, dependency limits, parallel data access, and worker shutdown.

17 drillsPractice one at a timeOrdered pathConcept questionComparison questionDebugging scenarioArchitecture scenario

Recommended start

Async/Await

Explain async/await as C# syntax over Task-based asynchronous work, with attention to non-blocking I/O and request throughput.

Easy~5 minStep 1 of 17

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1Async/AwaitRecommended startExplain async/await as C# syntax over Task-based asynchronous work, with attention to non-blocking I/O and request throughput.Concept questionEasy~5 min.NETASP.NET CoreC#Practice 2Async is not a new threadClarify the common misconception that await starts work on a new thread, and explain what actually happens for I/O-bound operations.Concept questionEasy~5 min.NETASP.NET CoreC#Practice 3Await internalsExplain the async state machine, continuation scheduling, and exception flow when a C# method awaits a Task.Concept questionMedium~7 min.NETASP.NET CoreC#Practice 4Task vs ThreadCompare Task and Thread in .NET, including abstraction level, scheduling, and when direct thread management is rarely appropriate.Comparison questionMedium~7 min.NETASP.NET CoreC#Practice 5Task.Run vs AwaitExplain when Task.Run is useful, when async/await is enough, and why Task.Run is usually wrong for I/O in ASP.NET Core.Comparison questionMedium~7 min.NETASP.NET CoreC#Practice 6Task.WhenAllUse Task.WhenAll to run independent asynchronous I/O operations concurrently while handling exceptions, cancellation, and dependency limits.Concept questionMedium~7 min.NETASP.NET CoreC#Practice 7WhenAll ExceptionsExplain how Task.WhenAll behaves when one or more tasks fail and how to inspect failures safely.Concept questionMedium~7 min.NETASP.NET CoreC#Practice 8CancellationTokenUse CancellationToken to stop wasted work when clients disconnect, timeouts expire, or background operations are being shut down.Concept questionMedium~7 min.NETASP.NET CoreC#Practice 9Timeout vs CancellationDistinguish timeouts from cancellation and explain how to combine them around external calls and request handling.Comparison questionMedium~7 min.NETASP.NET CoreC#Practice 10Fire-and-forget TasksExplain why starting background work without awaiting or tracking it is risky in ASP.NET Core applications.Concept questionMedium~7 min.NETASP.NET CoreC#Practice 11Sync-over-asyncInvestigate deadlocks or starvation caused by blocking on async code with Result, Wait, or GetAwaiter().GetResult().Debugging scenarioHard~12 min.NETASP.NET CoreC#Practice 12Thread Pool StarvationDiagnose thread-pool starvation caused by blocking work, unbounded concurrency, or sync-over-async in .NET APIs.Debugging scenarioHard~12 min.NETASP.NET CoreC#Practice 13Race ConditionsInvestigate and fix a race condition caused by shared mutable state in a .NET service.Debugging scenarioMedium~10 min.NETASP.NET CoreC#Practice 14lock vs SemaphoreSlimCompare lock and SemaphoreSlim for protecting shared state and coordinating async workflows.Comparison questionMedium~7 min.NETASP.NET CoreC#Practice 15Limit External CallsDesign a bounded-concurrency approach for calling an external API safely from .NET code.Architecture scenarioMedium~10 min.NETASP.NET CoreC#Practice 16DbContext and parallel workDiagnoses thread-unsafe scoped dependencies inside parallel execution and redesigns the data boundary without exhausting shared resources.Debugging scenarioHard~12 min.NETASP.NET CoreC#Practice 17BackgroundService ShutdownExplain how a .NET BackgroundService should handle cancellation, in-flight work, and application shutdown.Debugging scenarioMedium~10 min.NETASP.NET CoreC#Practice

Practice order

17 drillsOne at a time

1Async/AwaitUp next / Easy / ~5 min
2Async is not a new threadEasy / ~5 min
3Await internalsMedium / ~7 min
4Task vs ThreadMedium / ~7 min
5Task.Run vs AwaitMedium / ~7 min
6Task.WhenAllMedium / ~7 min
7WhenAll ExceptionsMedium / ~7 min
8CancellationTokenMedium / ~7 min

+9 more drills in this section