Hidden Features of C#?

This came to my mind after I learned the following from this question:

where T : struct

We, C# developers, all know the basics of C#. I mean declarations, conditionals, loops, operators, etc.

Some of us even mastered the stuff like Generics, anonymous types, lambdas, LINQ, ...

But what are the most hidden features or tricks of C# that even C# fans, addicts, experts barely know?

Keywords

Attributes

Syntax

Language Features

Visual Studio Features

Framework

Methods and Properties

Tips & Tricks

• Nice method for event handlers by Andreas H.R. Nilsson


• Uppercase comparisons by John


• Access anonymous types without reflection by dp


• A quick way to lazily instantiate collection properties by Will


• JavaScript-like anonymous inline-functions by roosteronacid

Other