Hidden Features of C#? [closed]

Question

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?

Here are the revealed features so far:

Keywords

• yield by Michael Stum
• var by Michael Stum
• using() statement by kokos
• readonly by kokos
• as by Mike Stone
• as / is by Ed Swangren
• as / is (improved) by Rocketpants
• default by deathofrats
• global:: by pzycoman
• using() blocks by AlexCuse
• volatile by Jakub Šturc
• extern alias by Jakub Šturc

Attributes

• DefaultValueAttribute by Michael Stum
• ObsoleteAttribute by DannySmurf
• DebuggerDisplayAttribute by Stu
• DebuggerBrowsable and DebuggerStepThrough by bdukes
• ThreadStaticAttribute by marxidad
• FlagsAttribute by Martin Clarke
• ConditionalAttribute by AndrewBurns

Syntax

• ?? (coalesce nulls) operator by kokos
• Number flaggings by Nick Berardi
• where T:new by Lars Mæhlum
• Implicit generics by Keith
• One-parameter lambdas by Keith
• Auto properties by Keith
• Namespace aliases by Keith
• Verbatim string literals with @ by Patrick
• enum values by lfoust
• @variablenames by marxidad
• event operators by marxidad
• Format string brackets by Portman
• Property accessor accessibility modifiers by xanadont
• Conditional (ternary) operator (?:) by JasonS
• checked and unchecked operators by Binoj Antony
• implicit and explicit operators by Flory

Language Features

• Nullable types by Brad Barker
• Anonymous types by Keith
• __makeref __reftype __refvalue by Judah Himango
• Object initializers by lomaxx
• Format strings by David in Dakota
• Extension Methods by marxidad
• partial methods by Jon Erickson
• Preprocessor directives by John Asbeck
• DEBUG pre-processor directive by Robert Durgin
• Operator overloading by SefBkn
• Type inferrence by chakrit
• Boolean operators taken to next level by Rob Gough
• Pass value-type variable as interface without boxing by Roman Boiko
• Programmatically determine declared variable type by Roman Boiko
• Static Constructors by Chris
• Easier-on-the-eyes / condensed ORM-mapping using LINQ by roosteronacid
• __arglist by Zac Bowling

Visual Studio Features

• Select block of text in editor by Himadri
• Snippets by DannySmurf

Framework

• TransactionScope by KiwiBastard
• DependantTransaction by KiwiBastard
• Nullable<T> by IainMH
• Mutex by Diago
• System.IO.Path by ageektrapped
• WeakReference by Juan Manuel

Methods and Properties

• String.IsNullOrEmpty() method by KiwiBastard
• List.ForEach() method by KiwiBastard
• BeginInvoke(), EndInvoke() methods by Will Dean
• Nullable<T>.HasValue and Nullable<T>.Value properties by Rismo
• GetValueOrDefault method by John Sheehan

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

• netmodules by kokos
• LINQBridge by Duncan Smart
• Parallel Extensions by Joel Coehoorn

Answer 1

I didn't know the "as" keyword for quite a while.

MyClass myObject = (MyClass) obj;

vs

MyClass myObject = obj as MyClass;

The second will return null if obj isn't a MyClass, rather than throw a class cast exception.

Answer 2

Here's a useful one for regular expressions and file paths:

"c:\\program files\\oldway"
@"c:\program file\newway"

The @ tells the compiler to ignore any escape characters in a string.

Answer 3

lambdas and type inferrence are underrated. Lambdas can have multiple statements and they double as a compatible delegate object automatically (just make sure the signature match) as in:

Console.CancelKeyPress +=
    (sender, e) => {
        Console.WriteLine("CTRL+C detected!\n");
        e.Cancel = true;
    };

Note that I don't have a new CancellationEventHandler nor do I have to specify types of sender and e, they're inferable from the event. Which is why this is less cumbersome to writing the whole delegate (blah blah) which also requires you to specify types of parameters.

Lambdas don't need to return anything and type inference is extremely powerful in context like this.

And BTW, you can always return Lambdas that make Lambdas in the functional programming sense. For example, here's a lambda that makes a lambda that handles a Button.Click event:

Func<int, int, EventHandler> makeHandler =
    (dx, dy) => (sender, e) => {
        var btn = (Button) sender;
        btn.Top += dy;
        btn.Left += dx;
    };

btnUp.Click += makeHandler(0, -1);
btnDown.Click += makeHandler(0, 1);
btnLeft.Click += makeHandler(-1, 0);
btnRight.Click += makeHandler(1, 0);

Note the chaining: (dx, dy) => (sender, e) =>

Now that's why I'm happy to have taken the functional programming class :-)

Other than the pointers in C, I think it's the other fundamental thing you should learn :-)

Answer 4

Environment.NewLine

for system independent newlines.

Answer 5

If you want to exit your program without calling any finally blocks or finalizers use FailFast:

Environment.FailFast()

Answer 6

1. ?? - coalescing operator
2. using (statement / directive) - great keyword that can be used for more than just calling Dispose
3. readonly - should be used more
4. netmodules - too bad there's no support in Visual Studio