CODEWITHSUNDEEP
async-awaitnservicebus
Slava
Slava

Reputation: 6640

What's the difference between these two nservicebus statements

In one documentation they say IHandleMessages handler hast to be written this way (signature is automatically generated when I choose to "Implement interface" option in Visual Studio):

public class PlaceOrderHandler : IHandleMessages<PlaceOrder>
{
    public Task Handle(PlaceOrder message, IMessageHandlerContext context)
    {
        var orderPlaced = new OrderPlaced { OrderId = message.OrderId };

        return context.Publish(orderPlaced);
    }
}

While another documentation says it has to be written this way:

public class PlaceOrderHandler : IHandleMessages<PlaceOrder>
{
    public async Task Handle(PlaceOrder message, IMessageHandlerContext context)
    {
        var orderPlaced = new OrderPlaced { OrderId = message.OrderId };

        await context.Publish<OrderPlaced>(e => { e.OrderId = message.OrderId; });

    }
}

I wonder what is the difference between these two statements, can someone explain in simple language?

Which option is the right one?

Upvotes: 0

Views: 197

Answers (1)

Sean Feldman
Sean Feldman

Reputation: 25994

Both are correct options. The difference between the two is how a single asynchronous operation is handles in the Handle method.

In the first case, a Task is returned as-is. In the second case, publishing is awaited within the Handle method. The difference? In the first case no async state machine is created by the compiler as the task of publishing returned back. In the second scenario, a state machine is created.

Which option is the right one to use? They are both correct options. If a method is called frequently and you care for the unnecessary allocations not to take place, returnng a single task without awaiting is more efficient.

Upvotes: 6

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