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File handling in C#

Posted by Puran Mehra Articles | Learn .NET July 15, 2009
In this article I have explained about file handing in C#.
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File handling in C#

 

File handling is an unmanaged resource in your application system. It is outside your application domain (unmanaged resource). It is not managed by CLR.

 

Data is stored in two ways, persistent and non-persistent manner.

 

When you open a file for reading or writing, it becomes stream.

 

Stream: Stream is a sequence of bytes traveling from a source to a destination over a communication path.

 

The two basic streams are input and output streams. Input stream is used to read and output stream is used to write.

 

The System.IO namespace includes various classes for file handling.

 

The parent class of file processing is stream. Stream is an abstract class, which is used as the parent of the classes that actually implement the necessary operations.

 

The primary support of a file as an object is provided by a .NET Framework class called File. This static class is equipped with various types of (static) methods to create, save, open, copy, move, delete, or check the existence of a file.

 

Diagram to represent file-handling class hierarchy
 

 file_handling.gif

 

Note: FileIno, DirectoryInfo and DriveInfo classes have instance methods. File, Directory, Path classes have static methods.

 

The following table describes some commonly used classes in the System.IO namespace.

 

Class Name

Description

FileStream

It is used to read from and write to any location within a file

BinaryReader

It is used to read primitive data types from a binary stream

BinaryWriter

It is used to write primitive data types in binary format

StreamReader

It is used to read characters from a byte Stream

StreamWriter

It is used to write characters to a stream.

StringReader

It is used to read from a string buffer

StringWriter

It is used to write into a string buffer

DirectoryInfo

It is used to perform operations on directories

FileInfo

It is used to perform operations on files

 

Reading and writing in the text file

 

StreamWriter Class

 

The StreamWriter class in inherited from the abstract class TextWriter. The TextWriter class represents a writer, which can write a series of characters.

 

The following table describes some of the methods used by StreamWriter class.

 

Methods

Description

Close

Closes the current StreamWriter object and the underlying stream

Flush

Clears all buffers for the current writer and causes any buffered data to be written to the underlying stream

Write

Writes to the stream

WriteLine

Writes data specified by the overloaded parameters, followed by end of line

 

Program to write user input to a file using StreamWriter Class

 

using System;

using System.Text;

using System.IO;

 

namespace FileWriting_SW

{

    class Program

    {

        class FileWrite

        {

            public void WriteData()

            {

                FileStream fs = new FileStream("c:\\test.txt", FileMode.Append, FileAccess.Write);

                StreamWriter sw = new StreamWriter(fs);

                Console.WriteLine("Enter the text which you want to write to the file");

                string str = Console.ReadLine();

                sw.WriteLine(str);

                sw.Flush();

                sw.Close();

                fs.Close();

            }

        }

        static void Main(string[] args)

        {

            FileWrite wr = new FileWrite();

            wr.WriteData();

        }

    }

}

 

StreamReader Class

 

The StreamReader class is inherited from the abstract class TextReader. The TextReader class represents a reader, which can read series of characters.

 

The following table describes some methods of the StreamReader class.

 

Methods

Description

Close

Closes the object of StreamReader class and the underlying stream, and release any system resources associated with the reader

Peek

Returns the next available character but doesn't consume it

Read

Reads the next character or the next set of characters from the stream

ReadLine

Reads a line of characters from the current stream and returns data as a string

Seek

Allows the read/write position to be moved to any position with the file

 

Program to read from a file using StreamReader Class

 

using System;

using System.IO;

 

namespace FileReading_SR

{

    class Program

    {

        class FileRead

        {

            public void ReadData()

            {

                FileStream fs = new FileStream("c:\\test.txt", FileMode.Open, FileAccess.Read);

                StreamReader sr = new StreamReader(fs);

                Console.WriteLine("Program to show content of test file");

                sr.BaseStream.Seek(0, SeekOrigin.Begin);

                string str = sr.ReadLine();

                while (str != null)

                {

                    Console.WriteLine(str);

                    str = sr.ReadLine();

                }

                Console.ReadLine();

                sr.Close();

                fs.Close();

            }

        }

        static void Main(string[] args)

        {

            FileRead wr = new FileRead();

            wr.ReadData();

 

        }

    }

}

 

I hope that this article would have helped you in understanding file handling.

 

Your feedback and constructive contributions are welcome. Please feel free to contact me for feedback or comments you may have about this article.

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