Good Programming practices
1. Avoid passing data between screens using “Get” parameter. Use POST method wherever possible.
2. Avoid writing very long methods. A method should typically have 1~40 lines of code. If a method has more than 40 lines of code, you must consider re factoring into separate methods.
3. Method name should tell what it does. Do not use misleading names. If the method name is obvious, there is no need of documentation explaining what the method does.
Good:
void savePhoneNumber ( String phoneNumber )
{
// Check for valid phone number format, then save phone number.
}
Not Good:
// This method will save the phone number.
void saveNumber ( string aNumber )
{
// Save the phone number.
}
4. A method should do only ‘one job’. Do not combine more than one job in a single method, even if those jobs are very small.
Good:
// Save the address.
// saveEmailAddress ( emailAddress);
// Send an email to the supervisor to inform that the address is updated.
// sendEmail ( emailAddress );
Not Good:
// Save address and send an email to the supervisor to inform that
// the address is updated.
// updateEmailAndNotify( address, email );
void updateEmailAndNotify ( String address, String email )
{
// Job 1.
// Save the address.
// ...
// Job 2.
// Send an email to inform the supervisor that the address is changed.
// ...
}
5. Always watch for unexpected values. For example, if you are using a parameter with 2 possible values, never assume that if one is not matching then the only possibility is the other value.
Good:
If ( memberType == eMemberTypes.Registered )
{
// Registered user… do something…
}
else if ( memberType == eMemberTypes.Guest )
{
// Guest user... do something…
}
else
{
// Un expected user type. Throw an exception
throw new Exception (“Unexpected value “ + memberType.toString());
// If we introduce a new user type in future, we can easily find
// the problem here.
}
Not Good:
If ( memberType == eMemberTypes.Registered )
{
// Registered user… do something…
}
else
{
// Guest user... do something…
// If we introduce another user type in future, this code will
// fail and will not be noticed.
}
6. Do not hardcode numbers. Use constants instead. Declare constant in the top of the file and use it in your code.
However, using constants are also not recommended. You should use the constants in a config file or database so that you can change it later. Declare them as constants only if you are sure this value will never need to be changed.
7. Do not hardcode strings. Use resource files.
if(string.Compare(name,“john”,false) == 0)
{
//… name equals to john
}
10. Use String.isEmpty() instead of “” whenever possible.
11. Avoid using member variables. Declare local variables wherever necessary and pass it to other methods instead of sharing a member variable between methods. If you share a member variable between methods, it will be difficult to track which method changed the value and when.
12. Use enum wherever required. Explicitly assign values starting with None = 0 .
Good:
enum MailType {
None=0,
Html = 1,
PlainText =2,
Attachment =3
}
void SendMail (String message, MailType mailType) {
switch ( mailType ) {
case MailType.Html: // Do something break;
case MailType.PlainText: // Do something break;
case MailType.Attachment: // Do something break;
default:
// Do something break;
}
}
Not Good:
void sendMail (String message, String mailType)
{
switch ( mailType )
{
case "Html":
// Do something break;
case "PlainText":
// Do something break;
case "Attachment":
// Do something break;
default:
// Do something break;
}
}
12. Do not make the member variables public or protected. Keep them private and expose public/protected Properties.
13. The event handler should not contain the code to perform the required action. Rather call another method from the event handler.
14. Do not programmatically click a button to execute the same action you have written in the button click event. Rather, call the same method which is called by the button click event handler.
15. Never hardcode a path or drive name in code. Get the application path programmatically and use relative path.
16. Never assume that your code will run from drive “C:”. You may never know, some users may run it from network or from a “Z:”.
17. If a wrong value found in the configuration file, application should throw an error or give a message and also should tell the user what are the correct values.
18. Error messages should help the user to solve the problem if it is of an expected origin. Never give error messages like “Error in Application”, “There is an error” etc. Instead give specific messages like “Failed to update database. Please make sure the login id and password are correct.”
19. When displaying error messages, in addition to telling what is wrong, the message should also tell what the user should do to solve the problem. Instead of message like “Failed to update database.”, suggest what should the user do: “Failed to update database. Please make sure the login id and password are correct.”
20. Show short and friendly message to the user. But log the actual error with all possible information. This will help a lot in diagnosing problems.
21. Whenever possible, do not have more than one class in a single file.
22. Avoid having very large files. If a single file has more than 1000 lines of code, it is a good candidate for refactoring. Split them logically into two or more classes.
23. Avoid public methods and properties, unless they really need to be accessed from outside the class.
24. Avoid passing too many parameters to a method. If you have more than 4~5 parameters, it is a good candidate to define a class or structure.
25. If you have a method returning a collection, return an empty collection instead of null, if you have no data to return. For example, if you have a method returning an ArrayList, always return a valid ArrayList. If you have no items to return, then return a valid ArrayList with 0 items. This will make it easy for the calling application to just check for the “count” rather than doing an additional check for “null”.
26. Logically organize all your files within appropriate folders. Use 2 level folder hierarchies. You can have up to 10 folders in the root folder and each folder can have up to 5 sub folders. If you have too many folders than cannot be accommodated with the above mentioned 2 level hierarchy, you may need re factoring into multiple packagesd.
27. A good logging class needs to be create, which can be configured to log errors, warning or traces. If you configure to log errors, it should only log errors. But if you configure to log traces, it should record all (errors, warnings and trace). The log class should be written such a way that in future you can change it easily to log to Windows Event Log, SQL Server, or Email to administrator or to a File etc without any change in any other part of the application. Use the log class extensively throughout the code to record errors, warning and even trace messages that can help you trouble shoot a problem.
28. Declare variables as close as possible to where it is first used. Use one variable declaration per line. Do not declare all variables at the top of the function.
29. Use StringBuilder class instead of String when you have to manipulate string objects in a loop.
Consider the following example:
public String composeMessage (String[] lines)
{
String message = “”;
for (int i = 0; i < lines.Length; i++)
{
message += lines [i];
}
return message;
}
In the above example, it may look like we are just appending to the string object ‘message’. But what is happening in reality is, the string object is discarded in each iteration and recreated and appending the line to it.
If your loop has several iterations, then it is a good idea to use StringBuilder class instead of String object.
See the example where the String object is replaced with StringBuilder.
public String composeMessage (String[] lines)
{
StringBuilder message = new StringBuilder();
for (int i = 0; i < lines.Length; i++)
{
message.append( lines[i] );
}
return message.toString();
}
30. Use Conditional operator (?:) instead of if else condition for assigning a value based on a given criteria where applicable
Eg: allNumberTabs = fragments.Contains('A') ? "1" : "0";
31. Whenever possible, use non synchronized data structures instead of their synchronized alternatives. E.g : Use StringBuilder instead of StringBuffer if there is no need for synchronization.
32. Do not comment out code as the code is being refactored. Rather, delete the code to reduce confusion for later maintenance. The old code can always be retrieved from Source Control.
