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
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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
...
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
intelligence.
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.
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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.
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