1. Introduction................................................................................................................. 2
2. Purpose of coding standards and best practices.......................................................... 2
3. How to follow the standards across the team............................................................. 2
4. Naming Conventions and Standards........................................................................... 3
5. Indentation and Spacing............................................................................................. 6
6. Good Programming practices...................................................................................... 8
7. Architecture............................................................................................................... 14
8. ASP.NET................................................................................................................... 14
9. Comments.................................................................................................................. 14
10. Exception Handling................................................................................................... 15
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”!)
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
|
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.
