Introducing the Command Line Parser Library to make parsing command line arguments easier

November 10, 2015 3 Comments

If you’ve worked extensively with .NET console applications then you’ve probably encountered difficulties with parsing the command line arguments. They are passed into the args argument of the Main function. Then it’s your task to investigate if the caller has passed in all necessary arguments:

  • Have all the mandatory arguments been passed in?
  • What default value do we take for optional arguments?
  • What about the ordering of arguments?

…et cetera, the list could grow a lot longer.

Fortunately there are libraries that can help you parse the arguments. One such library is called Command Line Parser Library available from NuGet here. You can find its project page here with some initial code examples.

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Domain Driven Design with Web API extensions part 6: domain events with RabbitMq

November 9, 2015 2 Comments

Introduction

In the previous post we looked at some basic theory behind messaging between independent applications. We discussed a couple of options to solve the problem. In this post we’ll start building our messaging environment using RabbitMq.

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Python language basics 62: clean-up after exceptions with finally

November 8, 2015 Leave a comment

Introduction

In the previous post we discussed how to re-raise an exception using the raise keyword. You can use “raise” in order to re-throw the most recent exception with all its details so that it’s not silently suppressed or replaced with another exception which lacks the necessary details in order to locate bugs.

In this post we’ll see how to run a code block irrespective of whether an exception was raised or not.

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Python language basics 61: raising exceptions

November 7, 2015 1 Comment

Introduction

In the previous post we saw how to extract some useful information from an exception in Python. We discussed how to store the exception in a variable using an “as” clause and how to read its type and arguments.

In this post we’ll see how to use the “raise” keyword to re-raise or re-throw an exception.

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Exception handling in the .NET Task Parallel Library with C#: a safety catch-all

November 6, 2015 2 Comments

Introduction

There can be situations that your application uses threads to such an extent that you either cannot put a try-catch block around every single Task.Wait, Task.WaitAll etc. calls or you simply forget it. There is a way to subscribe to all unhandled aggregate exceptions that the task scheduler encounters. You can then decide what to do with the exception there.

The task scheduler has an UnobservedTaskException event. It’s straightforward to subscribe to that even with the += operator.

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Domain Driven Design with Web API extensions part 5: domain events between independent systems

November 5, 2015 1 Comment

Introduction

In the previous post we looked at a solution on how elements of a .NET solution can communicate with each other using a mediator. The mediator keeps the publisher decoupled from the subscribers. Also, the mediator won’t have any knowledge of the event handlers, their exact types and what and how they will handle the messages from the domain objects.

The solution helps the email sending event handler read the domain event in case a user added a new or updated an existing load test. In this post we’ll direct our attention to messaging between independent applications. We’ll ultimately simulate that a financial application also wants to be notified of the load test domain events in order to calculate the monthly profits.

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A basic example of using the ExpandoObject for dynamic types in .NET C#

November 4, 2015 3 Comments

The ExpandoObject in the System.Dynamic namespace is an interesting option if you ever need to write dynamic objects in C#. Dynamic objects are ones that are not statically typed and whose properties and methods can be defined during runtime. I’ve come across this object while I was discovering the dynamic language runtime (DLR) features in .NET. We’ve seen an example of that in this post with the “dynamic” keyword.

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Divide an integer into groups with C#

November 3, 2015 2 Comments

Say you’d like to divide an integer, e.g. 20, into equal parts of 3 and distribute any remainder equally across the groups. The result of such an operation would be the following 3 integers:

7,7,6

20 can be divided into 3 equal parts of 6 and we have a remainder of 20 – 6 * 3 = 2. 2 is then added as 1 and 1 to the first two groups of 6. The result is a more or less equal distribution of the start integer.

The following function will perform just that:

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Domain Driven Design with Web API extensions part 4: domain events in code

November 2, 2015 1 Comment

Introduction

In the previous post we looked at some theory behind domain events. We said that domain events were events that happen within a domain and that other components of the system may be interested in. The domain becomes the publisher – or producer – and the listeners will be the subscribers, or consumers of the domain messages.

We established that we’d solve the communication of consumers and subscribers through a mediator which stands in between. Publishers and subscribers will stay decoupled that way.

In this post we’ll implement the theory in C# code.

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Python language basics 60: interrogating the exception

November 1, 2015 2 Comments

Introduction

In the previous post we saw a couple of ways to handle multiple exception types in the same except block. You can provide a list of exception types separated by a comma or you can have a generic handler where you catch the Exception type.

Exception handling is not as straightforward and easy as it first may seem. Therefore we’ll continue our discussion of the topic by ways of querying the exception object.

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