Video: Text Files in C# (Bulgarian)

Topics covered:

• What is Stream?
  • Stream Basics
• Reading Text Files
  • The StreamReader Class
• Writing Text Files
  • The StreamWriter Class
• Handling I/O Exceptions

Video (in Bulgarian)

Presentation Content

What Is Stream?

• Stream is the natural way to transfer data in the computer world
• To read or write a file, we open a stream connected to the file and access the data through the stream

Streams Basics

• Streams are used for reading and writing data into and from devices
• Streams are _ordered sequences of _ bytes
  • Provide consecutive access to its elements
• Different types of streams are available to access different data sources:
  • File access, network access, memory streams and others
• Streams are open before using them and closed after that

The StreamReader Class

• System.IO.StreamReader
  • The easiest way to read a text file
  • Implements methods for reading text lines and sequences of characters
  • Constructed by file name or other stream
    • Can specify the text encoding
    • For Cyrillic use UTF8
  • Works like Console.Read() / ReadLine() but over text files

StreamReader Methods

• _new _ StreamReader(fileName)
  • Constructor for creating reader from given file
• ReadLine()
  • Reads a single text line from the stream
  • Returns null when end-of-file is reached
• ReadToEnd()
  • Reads all the text until the end of the stream
• Close()
  • Closes the stream reader

Using StreamReader – Practices

• The StreamReader instances should always be closed by calling the Close() method
  • Otherwise system resources can be lost
• In C# the preferable way to close streams and readers is by the " using " construction
  • It automatically calls the Close() after the using construction is completed

The StreamWriter Class

• System.IO.StreamWriter
  • Similar to StreamReader , but instead of reading, it provides writing functionality
• Constructed by file name or other stream
  • Can define encoding
  • For Cyrillic use "UTF8 "

StreamWriter Methods

• Write ()
  • Writes string or other object to the stream
  • Like Console.Write ()
• WriteLine ()
  • Like Console.Write Line()
• Flush ()
  • Flushes the internal buffers to the hard drive
• AutoFlush
  • Flush the internal buffer after each writing

What is Exception?

• "An event that occurs during the execution of the program that disrupts the normal flow of instructions“ – definition by Google
  • Occurs when an operation can not be completed
• Exceptions tell that something unusual has happened, e. g. error or unexpected event
• I/O operations throw exceptions when operation cannot be performed (e.g. missing file)
  • When an exception is thrown, all operations after it are not processed

Summary

• Streams are the main I/O mechanismsin .NET
• The StreamReader class and ReadLine() method are used to read text files
• The StreamWriter class and WriteLine() method are used to write text files
• Always put file handling in using(…) block
• Exceptions are unusual events or error conditions
  • Can be handled by try-catch-finally blocks