Handling special/foreign language characters in c#

public string ConvertSpecialCharstoForeignChars(string str)
{
string strFormD = str.Normalize(NormalizationForm.FormD);
StringBuilder sbOutput = new StringBuilder();
for (int ich = 0; ich < strFormD.Length; ich++)
{
UnicodeCategory uc = CharUnicodeInfo.GetUnicodeCategory(strFormD[ich]);
if (uc != UnicodeCategory.NonSpacingMark)
{
sbOutput.Append(strFormD[ich]);
}
}
return sbOutput;
}

C# File Handling

Problem. You need to handle file IO in your application written in the C# programming language, utilizing the .NET framework's powerful methods. Test the methods in the System.IO namespace and also look at some performance issues. Solution. Here are many examples and some benchmarks of the System.IO namespace from the base class library.

1. Add using System.IO

First, the author's experience is that the .NET Framework provides excellent file handling/IO methods. They are optimized in the framework so that you don't need to hand-optimize buffer sizes or other mechanics. Make sure to include the IO namespace, as shown here.

//
// Include this namespace for all the examples.
//
using System.IO;

2. Various File methods in .NET

Here we see a table showing some of the most useful and popular File methods available. Many C# programmers use these methods quite extensively, particularly the ones dealing with lines and text.

File.ReadAllBytes
   Useful for files not stored as plain text.
   See example near the bottom.

File.ReadAllLines
   Microsoft: "Opens a file, reads all lines of the file with the
   specified encoding, and closes the file."
   [See the benchmark below]

File.ReadAllText
   Returns the contents of the text file at the specified path as
   a string. [See the benchmark below]

File.WriteAllBytes
   Not covered here.
   It can be used in conjunction with File.ReadAllBytes.

File.WriteAllLines
   Stores a string array in the specified file, overwriting the
   contents. Shown in an example below.

File.WriteAllText
   Writes the contents of a string to a text file.

File.AppendAllText
   Use to append the contents string to the file at path.
   Microsoft: "Appends the specified string to the file,
   creating the file if it doesn't already exist."

File.AppendText
   Not covered here in this article.
   You can also use standard StreamWriter code.

3. Reading lines with File.ReadAllLines

Here you want to read all the lines in from a file and place them in an array. The following code reads in each line in the file "file.txt" into an array. This is efficient code, but this article contains performance metrics later on.

~~~ Program that uses ReadAllLines (C#) ~~~

using System.IO;

class Program
{
   static void Main()
   {
       // Read in every line in specified file.
       // This will store all lines in an array in memory,
       // which you may not want or need.
       string[] lines = File.ReadAllLines("file.txt");
       foreach (string line in lines)
       {
           // Do something with line
           if (line.Length > 80)
           {
               // Example code
           }
       }
   }

---------------------------------------------------

4. Reading lines with StreamReader ReadLine

Here we see how to use the ReadLine method in a loop. This method is not part of the File static class, but it is in the System.IO namespace. We will compare it to the File.ReadAllLines method.

--- Program that uses ReadLine (C#) --- using System.IO; class Program { static void Main() { // Read in every line in the file. using (StreamReader reader = new StreamReader("file.txt")) { string line; while ((line = reader.ReadLine()) != null) { // Do something with line string[] parts = line.Split(','); } } } }

5. Benchmarking file handling methods

Here we compare several of the File and StreamReader methods. The goal of this benchmark is to help developers write code that is easy-to-understand and also very fast and resource-friendly. The following two graphs show how the above two code blocks perform.

~~~ File read benchmark for 52,930 lines ~~~ The test was repeated 200 times. StreamReader was faster. File.ReadAllLines: 28.226 ms Using StreamReader ReadLine: 17.543 ms [faster] ~~~ File read benchmark for 20 lines ~~~ The test was repeated 20000 times. StreamReader was faster. File.ReadAllLines: 0.487 ms Using StreamReader ReadLine: 0.480 ms [faster]

Results. StreamReader is much faster for large files with 10,000+ lines, but the difference for smaller files is negligable. As always, plan for varying sizes of files, and use File.ReadAllLines only when performance isn't critical.

6. File.ReadAllText and alternative

Here we want to resolve whether File.ReadAllText was performing well. To answer this, the ReadAllText method was benchmarked against StreamReader; the result was that on a 4 KB file it was almost 40% slower.

::: Program that uses ReadAllText and StreamReader (C#) ::: using System.IO; class Program { static void Main() { // A. // Read in file with File class. string text1 = File.ReadAllText("file.txt"); // B. // Alternative: use custom StreamReader method. string text2 = FileTools.ReadFileString("file.txt"); } } public static class FileTools { public static string ReadFileString(string path) { // Use StreamReader to consume the entire text file. using (StreamReader reader = new StreamReader(path)) { return reader.ReadToEnd(); } } }

StreamReader helper. In some projects, it would be worthwhile to use the above ReadFileString custom static method. In a project that opens hundreds of small files, it would save 0.1 milliseconds per file.

--- Benchmark of file text read methods (C#) --- File.ReadAllText: 155 ms FileTools.ReadFileString: 109 ms [faster]

7. Using List with File.ReadAllLines

Here we look at a usage of the List constructed type with file handling methods. List and ArrayList are extremely useful data structures for C# programmers, as they allow object collections to rapidly expand or shrink. Here we look at how you can use LINQ to get a List of lines from a file in one line.

~~~ Program that uses ReadAllLines with List (C#) ~~~ using System.Collections.Generic; using System.IO; using System.Linq; class Program { static void Main() { // Read in all lines in the file, and then convert to List with LINQ. List fileLines = File.ReadAllLines("file.txt").ToList(); } }

8. Counting lines with File.ReadAllLines

Here we need to count the number of lines in a file but don't want to write lots of code to do it. Note that the example here doesn't have ideal performance characteristics. We reference the Length property on the array returned. [

--- Program that counts lines (C#) --- using System.IO; class Program { static void Main() { // Another method of counting lines in a file. // This is NOT the most efficient way. It counts empty lines. int lineCount = File.ReadAllLines("file.txt").Length; } }

9. Checking lines in files

Here we look at a method that tests each line in a file using an imperative statement from LINQ. Does a line containing a specific string exist in the file? Maybe you want to see if a name or location exists in a line in the file. Here we can harness the power of LINQ to find any matching line. [See also the Contains method on the List type.]

--- Program that uses LINQ on file (C#) --- using System.IO; using System.Linq; class Program { static void Main() { // One way to see if a certain string is a line // in the specified file. Uses LINQ to count elements // (matching lines), and then sets |exists| to true // if more than 0 matches were found. bool exists = (from line in File.ReadAllLines("file.txt") where line == "Some line match" select line).Count() > 0; } }

10. Persisting data with File.WriteAllLines

Here we look at how you can write an array to a file. When you are done with your in-memory processing, you often need to write the data to disk. Fortunately, the File class offers an excellent WriteAllLines method. It receives the file path and then the array to write. This will replace all the file contents.

::: Program that writes array to file (C#) ::: using System.IO; class Program { static void Main() { // Write a string array to a file. string[] stringArray = new string[] { "cat", "dog", "arrow" }; File.WriteAllLines("file.txt", stringArray); } } ::: Output of the program ::: cat dog arrow

11. Appending text to files

Here we mention a way you can append text to files in a simple method. The previous example will replace the file's contents, but for a log file or error listing, we must append to the file. Note that we could read in the file, append to that in memory, and then write it out completely again, but that's slow.

12. Reading all bytes

Here we use File.ReadAllBytes to read in an image, PNG, to memory. One example usage of this sample is to cache an image in memory for performance. This works very well and greatly outperforms reading in the image each time.

=== Program that caches binary file (C#) === static class ImageCache { static byte[] _logoBytes; public static byte[] Logo { get { // Returns logo image bytes. if (_logoBytes == null) { _logoBytes = File.ReadAllBytes("Logo.png"); } return _logoBytes; } } }

13. Summary

Here we saw several methods and patterns for using System.IO in the C# programming language. The author's experience is that C# and .NET is excellent with file handling, and one benchmark he has seen measures it as even faster than C++ on Windows in its default configuration. Nearly every medium or larger size program will need to use file input/output, and this article provides a sampling of some of the clearest methods for this purpose.

}

Exception Handling

Exception Handling

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.

Beginners Must Read

Programming practices

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();
}


Architecture

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.

Programming Naming Conventions

Naming Conventions and Standards

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 ...

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.

CSharp Best Practices

C# Best Practices

Method to check whether input is interger or not

private bool IsInteger(string strInput)
{
try
{
int.parse(strInput);
return true;
}
catch(Exception ex)
{
return false;
}
}