Bits of .NET

Task allocates even when result is immediately available. ValueTask avoids allocation for synchronous returns.

Scenario:

// Cache that often has value ready (no async needed)
public async Task GetUserAsync(int id)
{
    if (_cache.TryGetValue(id, out var user))
        return user;  // Immediate return, but still allocates Task
    
    return await _db.Users.FindAsync(id);
}

Better with ValueTask:

public async ValueTask GetUserAsync(int id)
{
    if (_cache.TryGetValue(id, out var user))
        return user;  // No allocation when cached!
    
    return await _db.Users.FindAsync(id);
}

When to Use:
– Method often returns synchronously (cache hits)
– High-frequency calls (called millions of times)
– Performance-critical code

When NOT to Use:
– Method always awaits
– Result needs to be stored/passed around