ValueTask and ValueTask<T> for performance

Context: ValueTask and ValueTask<T> are structs that can reduce heap allocations when the result is often available synchronously.

using System.Collections.Generic;
using System.Threading.Tasks;

public class CacheExample
{
    private Dictionary<string, int> cache = new Dictionary<string, int>();

    public async ValueTask<int> GetCachedValueAsync(string key)
    {
        if (cache.TryGetValue(key, out int value))
            return value; // synchronous path, no allocation

        int result = await FetchFromDatabaseAsync(key);
        cache[key] = result;
        return result;
    }

    private async Task<int> FetchFromDatabaseAsync(string key)
    {
        await Task.Delay(100); // simulate database call
        return 42;
    }
}

When to use ValueTask

When the method often completes synchronously (cached results).
In high‑performance libraries to avoid unnecessary allocations.
For hot paths where you measure a performance gain.

Real-world usage example

Memory cache: A method that reads from an in‑memory cache (fast, synchronous) and falls back to an async database call.

Example: Microsoft.Extensions.Caching.Memory uses ValueTask for cache operations.

ValueTask and ValueTask<T> for performance

When to use ValueTask

Real-world usage example

Related sections