Bits of .NET

Loading all results into memory first is wasteful. IAsyncEnumerable streams results as they’re retrieved.

Old Way – Load Everything:

public async Task> GetOrdersAsync()
{
    return await _db.Orders.ToListAsync();
    // Loads all 1 million orders into memory!
}

// Caller:
var orders = await GetOrdersAsync();  // 5GB in memory
foreach (var order in orders)
    ProcessOrder(order);

Stream with IAsyncEnumerable:

public async IAsyncEnumerable GetOrdersAsync()
{
    await foreach (var order in _db.Orders.AsAsyncEnumerable())
    {
        yield return order;
    }
}

// Caller:
await foreach (var order in GetOrdersAsync())
{
    ProcessOrder(order);
    // Processes one at a time, low memory!
}

Benefits:
– Low memory usage
– Start processing immediately
– Can cancel mid-stream