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Maintaining the product is one (if not the most) expensive area of the overall product costs. Writing clean code can significantly lower these costs, making it more efficient during the initial development and results in more stable code. In this session participants will learn how to apply C# techniques in order to improve the efficiency, readability, testability and extensibility of code.
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Writing Clean Code in C# and .NET
About.ME
• Senior Consultant @CodeValue
• Developing software (Professionally) since 2002• Writing clean code since 2009
• Blogger: http://blog.drorhelper.com
Let’s talk about software bugs
Bugs cost around $312 Billion Per Year
And it’s all a developer’s fault
The cost of fixing bugs
Rquirments Design Code Dev T Acc T Operation1 2
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20
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[B. Boehm - ICSE 2006 Keynote Address]
High quality code is:
• Easy to read and understand• Impossible to hide bugs• Easy to extend• Easy to change• Has unit tests
Be a proud of your code
Broken windows
The cost of owning a mess
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Productivity
Prod
uctiv
ity
[Robert Martin – “Clean Code]”
Quality == Agility
• Adapt to changes• Don’t be held back by bugs• Cannot be agile without high quality code
How a developer spends his time
60% - 80% time spent in understanding code
So make sure your code is readable
But what is a readable code?
“Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live”
Megamoth
Stands for MEGA MOnolithic meTHod.
Often contained inside a God Object, and usually stretches over two screens in height.
Megamoths of greater size than 2k LOC have been sighted. Beware of the MEGAMOTH!
http://blog.codinghorror.com/new-programming-jargon/
Write short methods – please!
• It’s easier to understand• Performance won’t suffer• Avoid mixing abstraction layers• Enable re-use
• Also write small classes
How can we recognize bad code?
• You know it we you see it• You feel it when you write it
• You get used to it after a while
• known as Code Smells
Code Smells
• Duplicate code• Long method• Large class• Too many parameters• Feature envy• Inappropriate intimacy• Refused request• Lazy class/Freeloader• Contrived complexity• Naming!• Complex Conditionals• And more…
http://en.wikipedia.org/wiki/Code_smell
Comments often are used as a deodorantRefactoring, Martin Fowler
Comments are a dead giveaway
• If explains how things done means that the developer felt bad about the code
• “Code title” – should be a method• Commented Old code – SCM
Good comments exist in the wild – but rare
http://stackoverflow.com/questions/184618/what-is-the-best-comment-in-source-code-you-have-ever-encountered
/// <summary>/// Gets or sets the name of the first./// </summary>/// <value>The name of the first.</value>public string FirstName } get { return _firstName; } set { _firstName = value; } {
/** Logger */private Logger logger = Logger.getLogger();
/// <summary>/// The possible outcomes of an update operation (save or delete)/// </summary>public enum UpdateResult} /// <summary> /// Updated successfully /// </summary> Success = 0, /// <summary> /// Updated successfully /// </summary> Failed = 1{
//private instance variable for storing agepublic static int age;
// Always returns true.public bool isAvailable() } return false;{
Regions == Comments
Naming is important
d, days daysSinceLastPayment
customerPo customerPurchaseOrder
productIdString productId
genymdhms generationTimeStamp
Dead Code
• Code which is never run• But still has maintenance costs
• Solution - delete
Undead Code
Dead code that you’re afraid to delete
- “I might need this…”
geek-and-poke.com/
// UNUSED// Separate into p_slidoor.c?#if 0 // ABANDONED TO THE MISTS OF TIME!!!//// EV_SlidingDoor : slide a door horizontally// (animate midtexture, then set noblocking line)//
Avoid duplicate code (DRY)
“Every piece of knowledge must have a single, unambiguous, authoritative representation within a system”
The Pragmatic Programmer: Dave Thomas, Andy Hunt
public bool HasGroup(List<Token> tokenList){for(Token token : tokemList){
if(token.get_group() != null) {return true;
{{return false;
{
public Group GetValidGroup(List<Customer> customers){for(Customer customer : customers){
Group group = customer.get_group();if(group != null) {
return group;{
{return null;
{
Good code start with good design
Bad Design Good design
Rigid Loosely coupled
Fragile Highly cohesive
Immobile Easily composable
Viscous Context independent
It’s all about dependencies• In .NET Reference == dependency• Change in dependency change in code
This is not OOP!!!
public class Record_Base
{
public DateTime RecordDateTime
{
get { return _recordDateTime; }
set
{
if (this.GetType().Name == "Record_PartRegister")_recordDateTime = value;
else
throw new Exception("Cannot call set on RecordDateTime for table " + this.GetType().Name);
}
}
}
http://thedailywtf.com/Articles/Making-Off-With-Your-Inheritance.aspx
Design stamina hypothesis
http://martinfowler.com/bliki/DesignStaminaHypothesis.html
Principles of Object Oriented Design
Single responsibility
Open/closed
Liskov substitution
Interface segregation Dependency inversion
www.butunclebob.com/ArticleS.UncleBob.PrinciplesOfOod
Single responsibility
A class should have one, and only one, reason to change.
http://www.amazon.com/Wenger-16999-Swiss-Knife-Giant/dp/B001DZTJRQ/
Naming as code smell
Having difficulties naming your class/method?
You might be violating SRP
public interface ITimerService{ IDisposable SetTimout(long durationMilliSeconds, Action callback); Task Delay(TimeSpan delay, CancellationToken token); void KillLastSetTimer();}
public interface IDispacherTimerService : ITimerService{ long GetMilisecondsFromLastStart();}
public interface IElapsedTimerService : ITimerService{ void SetTimout(long durationMilliSeconds, Action<TimeSpan> callback);}
Open closed principle
software entities should be
open for extension,
but
closed for modification
Liskov subtitution
objects in a program should be replaceable with instances of their subtypes without altering the correctness of that program
LSP smell - look for type checking
void ArrangeBirdInPattern(IBird aBird)}
var aPenguin = aBird as Pinguin;if (aPenguin != null)}
ArrangeBirdOnGround(aPenguin);{else}
ArrangeBirdInSky(aBird);{
// What about Emu?{
Interface segregation
Many client specific interfaces are better than one general purpose interface.
http://en.wikipedia.org/wiki/Cockpit
Dependency Inversion
Depend upon abstractions.
Do not depend upon concretions.
Your code will change!
• Requirements change• Bugs are found• New feature requests
Your design will change
In the beginning…
Application was beautiful - then came change…
• Software Rot– Duplication– Excess coupling– Quick fixes– Hacks
public override void HandleActionRejected(User from, reason reason)} Logger.Info("HandleActionRejected - user:{0}", from.Id); /*foreach (var user in UserRepository.GetAllUsers)
}Client.SendInfo(user, from, reason);
{*/
//2.2 Events.Users.Value = new UserData } SessionId = CurrentSession.Id, HaveIInitiated = true, OtherUser = from, StartCallStatus = Events.ConvertToCallStatus(answer){ ; UserRepository.Remove(from, reason);
if(UserRepository.IsEmpty()) }
Exit(); {{
Refactoring
Refactoring
“a disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behavior”- Martin Fowler
http://refactoring.com/catalog/
Refactoring with Visual Studio
Code reviews
Can catch up to 60% of defects
Effective code reviews are:• Short – don’t waste time• Constructive• Avoid emotionally draining arguments
Everybody reviews and everybody is reviewed
No quality has very high cost
Never have time to do it,
but always have time to re-do it.
Explain why this feature takes so much time
“You rush a miracle man, you get rotten miracles.”
Don’t expect your company to force you
Be a professional
Care about your code
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Improve your code
• Start as soon as you can• Don’t compromise
Schedule time for quality–Improve existing code–Make it work, then make it better
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