Coding Standards

Coding Standards

Do conventions make difference in functionality? X1 = X1 - X2 XX = X2+ST( fi ); X1 = X1 + LF(X1, X2) + XX X1 = X+ IT(X1, X); OR balance = balance - lastPayment monthlyTotal = newPurchase+SalesTax(newPurchase); Balance= balance + LateFee(customer, balance) + monthlyTotal; balance = balance+ Interest(customerId, balance);

Naming variables

Naming methods t1 = calc1(); t2 = calc2(); S2 = calcAll(t1, t2); netPrice = CalculatePrice(); tax = CalculateTax(); sum = CalculateSum(netPrice, tax);

are comments the answer? // the total to = 0.0; // looping on line items // lt is total number of lines for( int i = 0 ; i < lt ; i++) { // adding line to total to = to + li(i); } total = 0.0 for (int line = 0 ; lines <linesTotal ; line++) { total = total + LineValue(line); }

“Any convention is better than no convention. The power of naming convention doesn’t come from the specific convention chosen but from the fact that a convention exists, adding structure to the code and giving you fewer things to worry about” Steve McConnell, Code Complete.

“Actual” Examples of hard to maintain code • InterChange.cs in the transactioSet.dll 7,059 lines of Code comparing to the consesus maximum of 300~400. • DeisgnerForm in the FormDesigner is 3,866 lines of code • BCC’s CalculateHcfa method: • 900 lines of code in ONE method • More than 50 local variables declared • Reading from a workflow message: if(((Kernel.PharmacyDl.PharmacyDl_Service_Lines_Loop)hMsg.L4_PharmacyDl_Service_Lines_Loop[piLineNo-1]).S1_Service_Lines_Segment.Count > 0) { ((Kernel.PharmacyDl.Service_Lines_Segment)((Kernel.PharmacyDl.PharmacyDl_Service_Lines_Loop)hMsg.L4_PharmacyDl_Service_Lines_Loop[piLineNo-1]).S1_Service_Lines_Segment[0]).E18_Accepted_Flag.ElementValue = psValue; }

When you should NOT care about sticking to a convention? • When you are sure no one else except you will ever have to work with that code. • When program is so small that you can remember all details in your head. • When you want the programmers working with you to be mad. 

Coding Guidelines consist of: • Naming guidelines: How to name namespaces/Classes/Methods/Properties/Variables,… • Programming Guidelines: raising and handling exceptions, class size, method size, best practices,..

Naming Guidelines Main Capitalization styles in .NET: • Pascal case The first letter in the identifier and the first letter of each subsequent concatenated word are capitalized. For example: BackColor • Camel case The first letter of an identifier is lowercase and the first letter of each subsequent concatenated word is capitalized. For example: backColor

Naming Guidelines General considerations: • Do NOT use abbreviations: GetPatient vs. GetPat • Do NOT use underscores. • Use Correctly spelled words • Avoid homonyms: IQ vs. EYEQ • NEVER use a single character variable unless as loop index. • Camel case for parameters and local variables. • Pascal Case for properties, Methods and Classes. • Always use CLEAR names that suggest the use of the field/prop./method/class. • Use only IT related acronyms: UI vs. GPC (which is a “known” acronym) • Research suggests that planning to use conventions after a “fast start” without conventions rarely works.

Programming Guidelines • Keep It Simple. The key point is to manage complexity. • You should be alarmed if • Class is more than 300~400 lines. • Method is more than 25 lines. • Ambiguous method names: getNum vs. GetPhoneNumber • Numbers are hardcode numbers. Use constants instead. • Strings/Paths/Messages are hardcoded. Use resource files instead. • Vague Error messages: Error in application vs. Error accessing DB.

Dealing with Exceptions • Methods should throw exceptions rather than return an error code. • Provide a method to check the condition to avoid the exception: • Example: provide a method IsFileExisting() so users will use it before LoadFile(). • Always throw the specific exception not the general Exception • Never use an empty catch • Always catch the specific exception • Stack Trace starts where exception is thrown not where is occurred: • Example: • Try • { some code causing exception} • Catch • { • Throw new exception vs. throw • }

Best Practices Always check the parameters at the beginning of the method. Rather than letting the problem propagate and make debugging much harder Example: Public void CheckClientAgeAtServiceDate(String name) { // code to get Client Data from DB // code to get service Data from DB String firstName = name.Substring(0); ---may throw null reference exception }

Best Practices Logging saves a lot of time in debugging: Example: Public void CalculateCartValue() { int numberOfItems = GetNumberOfItems(); log(“number of items = “ + numberOfItems); for ( int I = 0 ; I < numberOfItems; i++) { itemPrice = GetItemPrice(i); log(“price of item = “ + I +” is “itemPrice ); } }

Best Practices StringBuilder(dynamic) vs. String (immutable) Bad Example: String x = “”; For (int I = 0 ; I < 100 ; i++) { x = (String)array[i]; } Creates 100 Object • Good Example: StringBuilder x = new StringBuilder(“”) For (int I = 0 ; I < 100 ; i++) { x = (String)array[i]; } Creates 1 Object

Best Practicesusing Constants rather than literal strings • Bad String name = (String)hashtable(“name”); Or int columnId = dataReader.getOrdinal(“Name”); • Good Const string NameKey = “name”; String name = (String)hashtable(NameKey); Or int columnId = dataReader.getOrdinal(NameKey);

Tools • FxCop: http://www.gotdotnet.com/team/fxcop/ • FxCop is an application that analyzes managed code assemblies and reports information about the assemblies, such as possible design, localization, performance, naming, design rules and security improvements. • FxCop is FREE. • Available as standalone and built in VS 2005 • FxCop is intended for class library developers; however, anyone creating applications that should conform to .NET Framework best practices will benefit • Can be customized to check for additional custom rules

Main References: • .NET framework design guidelines by Microsoft @ http://msdn.microsoft.com/library/en-us/cpgenref/html/cpconnetframeworkdesignguidelines.asp • McConnell, Steve. 2004. Code Complete. Microsoft Press • http://www.dotnetspider.com/technology/tutorials/BestPractices.aspx

Bottom line:Use common sense and good judgment

Thank you!Emad Magdy

Coding Standards