Use ValueTask<T> in .NET

AbstractA quick note on when and why to use ValueTask<T> instead of Task<T> in .NET for high-throughput, cache-friendly async APIs.

Keywords:tech · c# · dotnet · async

Use ValueTask<T> when your async method often returns a result synchronously — it avoids unnecessary heap allocations and is faster under load.

The problem with `Task<T>`

Every Task<T> is a heap-allocated object. For methods that resolve synchronously most of the time (e.g., cache hits), this creates a lot of garbage for no real benefit.

The fix with `ValueTask<T>`

ValueTask<T> is a struct. When the result is already available, it returns inline — zero allocation.

internal interface ILookupService
{
    ValueTask<IList<LookupModel>> GetCategoriesAsync();
}

When to use it

Scenario	Use
Result often comes from cache (sync)	`ValueTask<T>`
Always awaits I/O (DB, HTTP)	`Task<T>`
Called in loop that service mostly returns sync results	`ValueTask<T>`

Don't use ValueTask<T> everywhere — only where performance profiling shows benefit

The problem with Task<T>

The fix with ValueTask<T>

When to use it

Cite

The problem with `Task<T>`

The fix with `ValueTask<T>`