Tips and tricks in C# .NET
September 23, 2016 Leave a comment
A Lookup in .NET is one of the lesser known data structures. It is similar to a Dictionary but the keys are not unique. You can insert multiple elements for the same key.
Say you have the following object and collection:
September 22, 2016 Leave a comment
Introduction
In the previous post we saw how to publish messages with MassTransit. Our demo register customer command listener publishes a customer registered event that any interested party can sign up to. An advantage with the setup is that the publisher has no knowledge of the consumers, they are completely decoupled. The opposite and more frequent case is often a manager application that knows exactly which parties should be notified and sends them a message directly.
In this post we’ll diverge a little from messaging techniques and look at dependency injection instead. We’re inte particular interested in how to inject a dependency into a registered command or event consumer.
September 21, 2016 Leave a comment
You’ve probably come across applications that warn you if the CapsLock button is pressed when typing a password. It’s a clever way to warn the user as passwords are normally not shown on the screen in plain text so it’s difficult to see what you’re typing. Similarly the NumLock button affects the behaviour of various keys on your keyboard.
Detecting whether those two special buttons are pressed is very simple in .NET console applications.
September 20, 2016 3 Comments
Introduction
In the previous post we got our hands dirty and started coding a small demo application around MassTransit. We managed to send a message from a publisher to a consumer using the MassTransit/RabbitMq client library. We saw a very basic configuration of the bus control and how to register a consumer for a message type. The message type can by convention be an event or a command. Both are best encapsulated in an interface with get-set properties and separate naming conventions. Therefore commands and events are not some special C# language features in this case. Instead, they are basic terminology in the world of messaging. Our first example centred around sending a single command using a single queue.
In this post we’ll extend our demo to publishing a message that can be consumed by multiple receivers. The goal is to publish a customer registered event from the register customer command consumer. The event will be consumed by 2 receivers that the event publisher will not have any knowledge of.
September 19, 2016 Leave a comment
In this post we saw how to add a declaration to an XML document. A well-formatted XML document starts with a declaration whose main function is to declare formally that the upcoming document is of the XML type. The XDeclaration object helps us to easily add a declaration to an XML document. Note that the XDocument.ToString method does not print the declaration for some reason so we need to print it separately if needed.
In this post we’ll see how to add a processing instruction to an XML document.
September 16, 2016 Leave a comment
In this post we saw how to add a namespace to an XML document. A namespace in XML is similar to the namespace in a programming language. It helps to avoid name clashes among nodes that can have similar names, like “Customer” which is quite a common domain. The fully qualified name of a node will be the namespace and the node name.
In this post we’ll see how to add a declaration to an XML document.
September 15, 2016 1 Comment
In this post we built a very simple XML document using LINQ to XML. We saw the 3 most frequently used objects in the System.Xml.Linq namespace: XDocument, XElement and XAttribute. These objects and their constructors allow the creation of XML documents in a more fluent fashion than it was possible with the original XML related objects in the System.Xml namespace.
In this post we’ll see how to add a namespace to an XML document.
September 14, 2016 1 Comment
Introduction
In the previous post we presented the topic of this series: using the MassTransit service bus implementation in .NET. We also discussed service buses in general, what they are, what they do and how they can help the developer concentrate on the “important” stuff in a project based around messaging instead of spending time on low-level messaging operations. This is not to say that a service bus is a must for a distributed system to work properly. The system may as well work with RabbitMq only without an extra level of abstraction on top of it. Therefore you must be careful with your design choices. This is especially true of full-blown ESBs – enterprise service buses – that cost a lot of money and introduce a high level of complexity in a distributed architecture.
In this post we’ll start writing code and send an object over the wire using MassTransit.
September 13, 2016 1 Comment
The GroupBy operator has the same function as GROUP BY in SQL: group elements in a sequence by a common key. The GroupBy operator comes with 8 different signatures. Each returns a sequence consisting of objects that implement the IGrouping interface of type K – the key type – and T – the type of the objects in the sequence. IGrouping implements IEnumerable of T. So when we iterate through the result the we can first look at the outer sequence of keys and then the inner sequence of each object with that key.
The simplest version of GroupBy accepts a Func delegate of T and K, which acts as the key selector. It will compare the objects in the sequence using a default comparer. E.g. if you want to group the objects by their integer IDs then you can let the default comparer do its job. Another version of GroupBy lets you supply your own comparer to define a custom grouping or if the Key is an object where you want to define your own rules for equality.
We’ll need an example sequence which has an ID. In the posts on LINQ we often take the following collections for the demos:
September 12, 2016 1 Comment
There are multiple ways to build a string out of other strings in .NET. Here come 5 of them.
Let’s start with the most obvious one that language learners encounter first, i.e. concatenation done by the ‘+’ operator:
string concatenatedOne = "This " + "is " + "a " + "concatenated " + "string.";
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