"objects" entries

Building C# objects dynamically

Using ExpandoObject to create objects that you can add properties, methods, and events to.

Buy “C# 6.0 Cookbook” in early release.
Editor’s note: This is an excerpt from “C# 6.0 Cookbook,” by Jay Hilyard and Stephen Teilhet. It offers more than 150 code recipes to common and not-so-common problems that C# programmers face every day. In it, you’ll find recipes on asynchronous methods, dynamic objects, enhanced error handling, the Rosyln compiler, and more.


You want to be able to build up an object to work with on the fly at runtime.


Use ExpandoObject to create an object that you can add properties, methods, and events to and be able to data bind to in a user interface.

We can use ExpandoObject to create an initial object to hold the Name and current Country of a person.

Once we have added properties directly, we can also add properties to our object in a more dynamic fashion using the AddProperty method we have provided for you. One example of why you might do this is to add properties to your object from another source of data. We will add the Language property.

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Python tuples: immutable but potentially changing

Think labels, not boxes

Python tuples have a surprising trait: they are immutable, but their values may change. This may happen when a tuple holds a reference to any mutable object, such as a list. If you need to explain this to a colleague who is new to Python, a good first step is to debunk the common notion that variables are like boxes where you store data.

In 1997 I took a summer course about Java at MIT. The professor, Lynn Andrea Stein — an award-winning computer science educator — made the point that the usual “variables as boxes” metaphor actually hinders the understanding of reference variables in OO languages. Python variables are like reference variables in Java, so it’s better to think of them as labels attached to objects.

Here is an example inspired by Lewis Carroll’s Through the Looking-Glass, and What Alice Found There.


Tweedledum and Tweedledee are twins. From the book: “Alice knew which was which in a moment, because one of them had ‘DUM’ embroidered on his collar, and the other ‘DEE’.”

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What it really means when people say “Everything in JavaScript is an object”

A new mantra for your next (programming) meditation session.

When you begin programming with JavaScript you might run across books, tutorials, and people who say “Everything in JavaScript is an object.” While it’s not 100% true (not *everything* is an object), it is *mostly* true. And sometimes this can be a bit surprising.

For instance, to most people functions and objects look and act completely different. And in many languages, functions and objects *are* completely different. However, in JavaScript, a function is an object. This can take a bit of concentrated attention to get your head around, but it’s an important concept because it’s the secret behind another big topic in JavaScript: functions as first class values.

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