Enterprise Service Bus libraries for .NET – NServiceBus

One in a series of posts giving a quick overview of ESB libraries for .NET

Originally an open-source library developed by Udi Dahan, the licensing was changed after version 2 to put it on a more commercial footing, and the software is now developed and supported by Udi’s company – Particular Software. The source code remains on Github.

NServiceBus is a tried and tested library. It has grown a lot since it’s humble beginnings and now is once part of a suite of tools and libraries for building distributed applications. It’s no surprise that Udi Dahan just happens to be highly regarded as an expert in distributed software architecture.

https://docs.particular.net/nservicebus/messaging/publish-subscribe/publish-handle-event

Messages

Messages need to either implement a marker interface or use defined conventions.

namespace Domain.Messages
{
  public class UserCreatedEvent : IEvent
  {
    public string Name { get; set; }
  }
}

Or

var conventions = endpointConfiguration.Conventions();

conventions.DefiningEventsAs(
 type =>

     {
       return type.Namespace == "MyNamespace.Messages.Events";
 });

Publishing

You can publish an event from within another handler or when you create an endpoint. This example shows publishing an event from an endpoint:

var endpointInstance = await Endpoint.Start(endpointConfiguration)
    .ConfigureAwait(false);
    await endpointInstance.Publish(new MyEvent())
      .ConfigureAwait(false);

Subscribing

To handle an event, implement IHandleMessages<T>

public class UserCreatedHandler : IHandleMessages<UserCreatedEvent>
{
  public Task Handle(UserCreatedEvent message, IMessageHandlerContext context)
  { … }
}

NServiceBus will automatically locate handlers by looking for implementations of IHandleMessages<T>

Enterprise Service Bus libraries for .NET

As a software application becomes larger, you may want to break it into separate parts, both to manage complexity but also to aid scalability. But if you break an application apart, how will the separate parts communicate? One approach is to employ messaging using a publish/subscribe (pub/sub) bus.

A few years ago, I worked on an application that used NServiceBus just for this purpose, but I thought it would be useful to survey the .NET landscape to find out what’s available today.

Here’s a summary of the libraries I’ll be looking at over the next few blog posts:

These libraries range from the relatively simple and tightly focused to the complete ‘enterprise-level’ configurable, extensible and/or fully supported.

Some of these libraries distinguish between an ‘event’ (notify subscribers that something has happened) and a ‘command’ (tell subscribers that they should perform an action). Some support long-running business processes, often known as ‘sagas’. Some support distributed transactions. Some use dependency injection and can integrate with an inversion-of-control container.

And because the feature sets vary so widely, I’ll just be highlighting how each library implements publishing an ‘event’ message, and how you subscribe to these messages.

Conditionally format rows in Excel depending on date range

Sometimes I get asked Excel questions. This is one of those times!

Given a spreadsheet with rows that contain a start and finish date, format the rows in the past, present and future in different colours, so that it looks like this:

I initially tried using a formula with Excel’s Conditional Formatting feature. Despite this being the recommended solution in some search results, I just found it set the one format for all the rows – not what I wanted. This post by Joseph D’Emanuele put me on the right track.

Here’s what I ended up doing:

1. Add a new column next to your existing data
2. In the first cell of this new column, insert the formula =IF(B2 < TODAY(), "Past", IF(A2 > TODAY(), "Future", "Current"))
3. Copy this formula down to the remaining rows. eg.
4. Now select all the rows you want to format (for me that’s A2:D5)
5. On the Home menu tab, select Conditional Formatting, then Manage Rules
6. You will add 3 rules – one for each status.
7. Click New Rule
8. Select Use a formula to determine which cells to format
9. In Format values where this formula is true, enter =INDIRECT(“D” &ROW()) = “Future”
10. Click Format and choose the desired formatting to apply for Future dates
11. Click OK and repeat adding new rules for “Current” and “Past”
12. You should end up with something like this:
13. Click OK and you should have rows formatted different colours depending on whether the start/finish date is in the past, current or in the future!
14. You can optionally choose to hide the Status row if you’d rather not see it all the time.

Note that the formula in the conditional formatting (=INDIRECT(“D” &ROW()) = “Future”) is hard-coded to the column – “D” in my case. If you move data around, you’ll need to update this to refer to the new column letter.