Anybody can write code. With a few months of programming experience, you can write 'working applications'. Making it work is easy, but doing it the right way requires more work, than just making it work.
Believe it, majority of the programmers write 'working code', but not ‘good code'. Writing 'good code' is an art and you must learn and practice it.
Everyone
may have different definitions for the term ‘good code’. In my definition, the
following are the characteristics of good code.
·
Reliable
·
Maintainable
·
Efficient
Most
of the developers are inclined towards writing code for higher performance,
compromising reliability and maintainability. But considering the long term ROI
(Return On Investment), efficiency and performance comes below reliability and
maintainability. If your code is not reliable and maintainable, you (and your
company) will be spending lot of time to identify issues, trying to understand
code etc throughout the life of your application.
To develop reliable and maintainable applications, you must follow
coding standards and best practices.
The naming conventions, coding standards and best practices
described in this document are compiled from our own experience and by
referring to various Microsoft and non Microsoft guidelines.
There are several standards exists in the programming industry.
None of them are wrong or bad and you may follow any of them. What is more
important is, selecting one standard approach and ensuring that everyone is
following it.
If
you have a team of different skills and tastes, you are going to have a tough
time convincing everyone to follow the same standards. The best approach is to have
a team meeting and developing your own standards document. You may use this
document as a template to prepare your own document.
Distribute
a copy of this document (or your own coding standard document) well ahead of
the coding standards meeting. All members should come to the meeting prepared
to discuss pros and cons of the various points in the document. Make sure you
have a manager present in the meeting to resolve conflicts.
Discuss
all points in the document. Everyone may have a different opinion about each
point, but at the end of the discussion, all members must agree upon the
standard you are going to follow. Prepare a new standards document with
appropriate changes based on the suggestions from all of the team members.
Print copies of it and post it in all workstations.
After
you start the development, you must schedule code review meetings to ensure
that everyone is following the rules. 3 types of code reviews are recommended:
- Peer review – another team member review the code to ensure that the code follows the coding standards and meets requirements. This level of review can include some unit testing also. Every file in the project must go through this process.
- Architect review – the architect of the team must review the core modules of the project to ensure that they adhere to the design and there is no “big” mistakes that can affect the project in the long run.
- Group review – randomly select one or more files and conduct a group review once in a week. Distribute a printed copy of the files to all team members 30 minutes before the meeting. Let them read and come up with points for discussion. In the group review meeting, use a projector to display the file content in the screen. Go through every sections of the code and let every member give their suggestions on how could that piece of code can be written in a better way. (Don’t forget to appreciate the developer for the good work and also make sure he does not get offended by the “group attack”!)
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Note :
The terms Pascal
Casing and Camel Casing are used throughout this document.
Pascal
Casing - First character of all words are Upper Case
and other characters are lower case.
Example: BackColor
Camel
Casing - First character of all words, except the
first word are Upper Case and other characters are lower case.
Example: backColor
|
1.
Use
Pascal casing for Class names
public class HelloWorld
{
...
}
2.
Use
Pascal casing for Method names
void SayHello(string name)
{
...
}
3.
Use
Camel casing for variables and method parameters
int totalCount = 0;
void SayHello(string name)
{
string fullMessage
= "Hello " + name;
...
}
4.
Use
the prefix “I” with Camel Casing for interfaces ( Example: IEntity )
5.
Do
not use Hungarian notation to name variables.
In
earlier days most of the programmers liked it - having the data type as a
prefix for the variable name and using m_ as prefix for member variables. Eg:
string m_sName;
int nAge;
However,
in .NET coding standards, this is not recommended. Usage of data type and m_ to
represent member variables should not be used. All variables should use camel
casing.
|
Some programmers still prefer to use the
prefix m_ to represent member variables, since there is no other easy
way to identify a member variable.
|
6.
Use
Meaningful, descriptive words to name variables. Do not use abbreviations.
Good:
string address
int salary
Not Good:
string nam
string addr
int sal
7.
Do
not use single character variable names like i, n, s etc. Use names like index, temp
One
exception in this case would be variables used for iterations in loops:
for ( int i = 0; i < count; i++ )
{
...
}
If
the variable is used only as a counter for iteration and is not used anywhere
else in the loop, many people still like to use a single char variable (i)
instead of inventing a different suitable name.
8.
Do
not use underscores (_) for local variable names.
9.
All
member variables must be prefixed with underscore (_) so that they can be
identified from other local variables.
10. Do not use variable
names that resemble keywords.
11. Prefix boolean variables,
properties and methods with “is” or similar prefixes.
Ex: private bool _isFinished
12. Namespace names
should follow the standard pattern
<company name>.<product name>.<top level
module>.<bottom level module>
13.
Use
appropriate prefix for the UI elements so that you can identify them from the
rest of the variables.
There are 2 different approaches recommended
here.
a.
Use
a common prefix ( ui_ ) for all UI elements. This will help you group all of
the UI elements together and easy to access all of them from the intellisense.
b.
Use
appropriate prefix for each of the ui element. A brief list is given below.
Since .NET has given several controls, you may have to arrive at a complete
list of standard prefixes for each of the controls (including third party
controls) you are using.
|
Control
|
Prefix
|
|
Label
|
lbl
|
|
TextBox
|
txt
|
|
DataGrid
|
dtg
|
|
Button
|
btn
|
|
ImageButton
|
imb
|
|
Hyperlink
|
hlk
|
|
DropDownList
|
ddl
|
|
ListBox
|
lst
|
|
DataList
|
dtl
|
|
Repeater
|
rep
|
|
Checkbox
|
chk
|
|
CheckBoxList
|
cbl
|
|
RadioButton
|
rdo
|
|
RadioButtonList
|
rbl
|
|
Image
|
img
|
|
Panel
|
pnl
|
|
PlaceHolder
|
phd
|
|
Table
|
tbl
|
|
Validators
|
val
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14. File name should
match with class name.
For
example, for the class HelloWorld, the file name should be helloworld.cs (or,
helloworld.vb)
15. Use Pascal Case for
file names.
1.
Use
TAB for indentation. Do not use SPACES. Define the Tab size as 4.
2.
Comments
should be in the same level as the code (use the same level of indentation).
Good:
// Format a message and
display
string fullMessage =
"Hello " + name;
DateTime currentTime =
DateTime.Now;
string message =
fullMessage + ", the time is : " + currentTime.ToShortTimeString();
MessageBox.Show ( message
);
Not Good:
// Format a message and
display
string
fullMessage = "Hello " + name;
DateTime
currentTime = DateTime.Now;
string message =
fullMessage + ", the time is : " + currentTime.ToShortTimeString();
MessageBox.Show
( message );
3.
Curly
braces ( {} ) should be in the same level as
the code outside the braces.
4.
Use
one blank line to separate logical groups of code.
Good:
bool SayHello ( string name )
{
string fullMessage = "Hello " + name;
DateTime currentTime = DateTime.Now;
string message = fullMessage + ", the time is :
" + currentTime.ToShortTimeString();
MessageBox.Show ( message );
if ( ... )
{
// Do something
// ...
return false;
}
return true;
}
Not
Good:
bool SayHello (string name)
{
string fullMessage = "Hello " + name;
DateTime currentTime = DateTime.Now;
string message = fullMessage + ", the time is :
" + currentTime.ToShortTimeString();
MessageBox.Show ( message );
if ( ... )
{
// Do something
// ...
return false;
}
return true;
}
5.
There
should be one and only one single blank line between each method inside the
class.
6.
The
curly braces should be on a separate line and not in the same line as if, for etc.
Good:
if ( ... )
{
// Do something
}
Not
Good:
if ( ... ) {
// Do something
}
7.
Use
a single space before and after each operator and brackets.
Good:
if ( showResult == true )
{
for ( int i = 0; i < 10; i++ )
{
//
}
}
Not
Good:
if(showResult==true)
{
for(int i= 0;i<10;i++)
{
//
}
}
8.
Use
#region to group related
pieces of code together. If you use proper grouping using #region, the page should
like this when all definitions are collapsed.
9.
Keep
private member variables, properties and methods in the top of the file and
public members in the bottom.
1.
Avoid
writing very long methods. A method should typically have 1~25 lines of code.
If a method has more than 25 lines of code, you must consider re factoring into
separate methods.
2.
Method
name should tell what it does. Do not use mis-leading names. If the method name
is obvious, there is no need of documentation explaining what the method does.
Good:
void SavePhoneNumber ( string phoneNumber )
{
// Save the phone number.
}
Not
Good:
// This method will save the phone number.
void SaveDetails ( string phoneNumber )
{
// Save the phone number.
}
3.
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.
SaveAddress ( address
);
// Send an email to the supervisor to inform that the address
is updated.
SendEmail ( address, email );
void SaveAddress ( string address )
{
// Save the address.
// ...
}
void SendEmail ( string address, string email )
{
// Send an email to inform the supervisor that the address
is changed.
// ...
}
Not
Good:
//
Save address and send an email to the supervisor to inform that
// the address is
updated.
SaveAddress
( address, email );
void
SaveAddress ( string address, string email )
{
//
Job 1.
//
Save the address.
//
...
//
Job 2.
//
Send an email to inform the supervisor that the address is changed.
//
...
}
4.
Use
the c# or VB.NET specific types (aliases), rather than the types defined in
System namespace.
int age; (not Int16)
string name; (not String)
object contactInfo; (not Object)
|
Some developers prefer to use types in Common Type System
than language specific aliases.
|
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 (“Un expected 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 the 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.
8.
Convert
strings to lowercase or upper case before comparing. This will ensure the
string will match even if the string being compared has a different case.
if ( name.ToLower() == “john” )
{
//…
}
9.
Use
String.Empty instead of “”
Good:
If ( name == String.Empty
)
{
// do something
}
Not
Good:
If ( name == “” )
{
// do something
}
10. 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.
11. Use enum wherever required.
Do not use numbers or strings to indicate discrete values.
Good:
enum MailType
{
Html,
PlainText,
Attachment
}
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. In the application
start up, do some kind of "self check" and ensure all required files
and dependancies are available in the expected locations. Check for database
connection in start up, if required. Give a friendly message to the user in
case of any problems.
18. If the required
configuration file is not found, application should be able to create one with
default values.
19. 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.
20. Error messages should
help the user to solve the problem. 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."
21. When displaying error
messages, in addition to telling what is wrong, the message should also tell
what should the user 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."
22. 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.
23. Do not have more than
one class in a single file.
24. Have your own
templates for each of the file types in Visual Studio. You can include your
company name, copy right information etc in the template. You can view or edit
the Visual Studio file templates in the folder C:\Program Files\Microsoft
Visual Studio 8\Common7\IDE\ItemTemplatesCache\CSharp\1033. (This folder has
the templates for C#, but you can easily find the corresponding folders or any
other language)
25. 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.
26.
Avoid
public methods and properties, unless they really need to be accessed from
outside the class. Use “internal” if they are accessed only within the same
assembly.
27.
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.
28.
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”.
29.
Use
the AssemblyInfo file to fill information like version number, description,
company name, copyright notice etc.
30.
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 assemblies.
16. Make sure you have a
good logging class 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). Your 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.
17. If you are opening
database connections, sockets, file stream etc, always close them in the finally block. This will
ensure that even if an exception occurs after opening the connection, it will
be safely closed in the finally block.
18. Declare variables as
close as possible to where it is first used. Use one variable declaration per
line.
19. Use StringBuilder
class instead of String when you have to manipulate string objects in a loop.
The String object works in weird way in .NET. Each time you append a string, it
is actually discarding the old string object and recreating a new object, which
is a relatively expensive operations.
Consider the following example:
public string
ComposeMessage (string[] lines)
{
string
message = String.Empty;
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();
}
1.
Always
use multi layer (N-Tier) architecture.
2.
Never
access database from the UI pages. Always have a data layer class which
performs all the database related tasks. This will help you support or migrate
to another database back end easily.
3.
Use
try-catch in your data layer to catch all database exceptions. This exception
handler should record all exceptions from the database. The details recorded
should include the name of the command being executed, stored proc name,
parameters, connection string used etc. After recording the exception, it could
be re thrown so that another layer in the application can catch it and take
appropriate action.
4.
Separate
your application into multiple assemblies. Group all independent utility
classes into a separate class library. All your database related files can be
in another class library.
1.
Do not use session variables throughout the code. Use
session variables only within the classes and expose methods to access the
value stored in the session variables. A class can access the session using System.Web.HttpCOntext.Current.Session
2.
Do
not store large objects in session. Storing large objects in session may
consume lot of server memory depending on the number of users.
3.
Always
use style sheet to control the look and feel of the pages. Never specify font
name and font size in any of the pages. Use appropriate style class. This will
help you to change the UI of your application easily in future. Also, if you
like to support customizing the UI for each customer, it is just a matter of
developing another style sheet for them
Good
and meaningful comments make code more maintainable. However,
1.
Do
not write comments for every line of code and every variable declared.
2.
Use
// or /// for comments. Avoid
using /*
… */
3.
Write
comments wherever required. But good readable code will require very less
comments. If all variables and method names are meaningful, that would make the
code very readable and will not need many comments.
4.
Do
not write comments if the code is easily understandable without comment. The
drawback of having lot of comments is, if you change the code and forget to
change the comment, it will lead to more confusion.
5.
Fewer
lines of comments will make the code more elegant. But if the code is not
clean/readable and there are less comments, that is worse.
6.
If
you have to use some complex or weird logic for any reason, document it very
well with sufficient comments.
7.
If
you initialize a numeric variable to a special number other than 0, -1 etc,
document the reason for choosing that value.
8.
The
bottom line is, write clean, readable code such a way that it doesn't need any
comments to understand.
9.
Perform
spelling
check on comments and also make sure proper grammar and punctuation is used.
1.
Never
do a 'catch exception and do nothing'. If you hide an exception, you will never
know if the exception happened or not. Lot of
developers uses this handy method to ignore non significant errors. You should
always try to avoid exceptions by checking all the error conditions
programmatically. In any case, catching an exception and doing nothing is not
allowed. In the worst case, you should log the exception and proceed.
2.
In
case of exceptions, give a friendly message to the user, but log the actual
error with all possible details about the error, including the time it
occurred, method and class name etc.
3.
Always
catch only the specific exception, not generic exception.
Good:
void ReadFromFile ( string fileName )
{
try
{
// read from file.
}
catch (FileIOException ex)
{
// log error.
//
re-throw exception depending on your case.
throw;
}
}
Not
Good:
void ReadFromFile ( string
fileName )
{
try
{
// read from file.
}
catch (Exception ex)
{
// Catching general exception is bad...
we will never know whether
// it was a file error or some other
error.
// Here you are hiding an exception.
// In this case no one will ever know
that an exception happened.
return "";
}
}
4.
No
need to catch the general exception in all your methods. Leave it open and let
the application crash. This will help you find most of the errors during
development cycle. You can have an application level (thread level) error
handler where you can handle all general exceptions. In case of an 'unexpected
general error', this error handler should catch the exception and should log
the error in addition to giving a friendly message to the user before closing
the application, or allowing the user to 'ignore and proceed'.
5.
When
you re throw an exception, use the throw statement without specifying the original
exception. This way, the original call stack is preserved.
Good:
catch
{
// do
whatever you want to handle the exception
throw;
}
Not Good:
catch (Exception ex)
{
// do
whatever you want to handle the exception
throw ex;
}
6.
Do
not write try-catch in all your methods. Use it only if there is a possibility
that a specific exception may occur and it cannot be prevented by any other
means. For example, if you want to insert a record if it does not already
exists in database, you should try to select record using the key. Some
developers try to insert a record without checking if it already exists. If an
exception occurs, they will assume that the record already exists. This is
strictly not allowed. You should always explicitly check for errors rather than
waiting for exceptions to occur. On the other hand, you should always use
exception handlers while you communicate with external systems like network,
hardware devices etc. Such systems are subject to failure anytime and error
checking is not usually reliable. In those cases, you should use exception
handlers and try to recover from error.
7.
Do
not write very large try-catch blocks. If required, write separate try-catch
for each task you perform and enclose only the specific piece of code inside
the try-catch. This will help you find which piece of code generated the
exception and you can give specific error message to the user.
8. Write your own custom
exception classes if required in your application. Do not derive your custom
exceptions from the base class SystemException. Instead, inherit from
ApplicationException.
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