The .NET compiler is a terrific thing… After all, it turns your C# into an executable program!

One nice feature of the .NET compiler, which is becoming better each release, is inferred typing. I’d like to lay out a few short examples that might help you develop your programming standards and practices.

Inferring a type when creating an array.

// Create and initialize an array
var myArray = new int[] { 1, 2, 3 };

Becomes:

I came across a need at work today to re-implement some of the Output Caching for our MVC3 application which runs under .NET 4.0. I wanted to use standard Output Caching (via the OutputCacheAttribute class, why re-invent the well-working wheel?) but due to some of our requirements I needed more control over how my objects were cached. More specifically, I needed to cache them with a custom Cache Dependency. With a little bit of Google-Fu, I was delighted to learn of the Output Cache Provider functionality introduced in ASP.NET 4. I implemented a custom OutputCacheProvider, registered it in my Web.config file as the Default Cache Provider, and I was well on my way.

As of .NET 3.0, LINQ (and the often related Lambda Expressions) have been available for our use and abuse. LINQ stands for Language INtegrated Query, and is a method of modelling OO data in a more or less relational sense that is not unlike databases. And just like databases, it comes with a cost.

To offset this cost, LINQ uses Deferred Execution. Deferred Execution means that the code is not executed until it is needed. This means that the LINQ code that you write is not actually executed until you NEED to execute it – typically during an enumeration of the results.

The topic at hand is interning. More specifically, string interning.

“What is string interning?” you ask? Good question. As you may or may not know, strings are immutable reference types. This means that they are read-only and a pointer will refer to the string’s location on the heap. Typically, a new string is created and stored within your application’s memory each time that you assign a string – even if the same string is defined repeatedly. What this means is that you can define the same string N times and have it take up the string’s memory N times. This sucks when dealing with repeating string data.

Something which I feel carries a lot of confusion in the .NET realm is virtual methods. During interviews, I tend to ask candidates about virtual methods: why and when they’d use one, what the purposes is, how a virtual method “works” under the hood, and how it differs from “shadowing”. Surprisingly, in what has probably been over one hundred interviews with senior-ish candidates, I don’t believe that more than one or two of them have answered anything about virtual methods correctly. From this I conclude that the understanding of virtual methods is not strong among the typical developer… And so, let us dive in.

I’m a bit tipsy at the moment, so hopefully this post goes well.

A question that I like to ask while interviewing individuals is: “why would you want to use an interface?” I get a ton of answers that span the supposed gamut of programming; some are good and some are of course terrible, however I’d like to share some input on what I feel is the importance of interfaces.

This is my first post. I hope that it doesn’t suck.

As of .NET 2.0, Microsoft introduced the concept of generics. Generics is a concept that allow you to “template” methods and types such as classes and interfaces in a (generally) type-safe way. Upon compilation, generic type metadata is stored in IL, and JIT’d as you reference the generic method or class with an actual type at runtime. Value types each get their own “copy” of the JIT’d generic code, whereas reference types share a single instance of the code. This is because the generic implementation is identical for reference types – they’re all just pointers.