C# tutorial-C# File Stream: Random-Access File

File Stream in C#



Random-Access File


The records in random-access file can be accessed directly and quickly without searching through a large number of records as in the case of sequential-access file. Random-access file is used in instant access systems such as banking system, sale system, air-line reservation system, etc.

Writing to and reading from a random-access file
 

In the example below, we write information of students to a file and read from it. Each information of a student are stored in a Student object generated from a Student class. The information of every student contains student number and student name. To write to and read from an random-access file, you can use BinaryWriter class and BinaryReader class. In the random-access file, you can specify the location to write data in or read data from using the position property of the FileStream class.

Example:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace ConsoleApplication1
{
class Program
{
public static int pos=0;
static void Main(string[] args)
{
readFromFile("D:\\student.txt");
addrecord();

}


class Student
{

private string stnumber;
private string stname;
private int recordsize;


public string stunumber
{ //stunumber property

set { stnumber = value; }
get { return stnumber; }



}
public string stuname
{ //stuname property

set { stname = value; }
get { return stname; }



}

public int size
{

get { return calsize(); }
}
private int calsize()
{
recordsize = 2 * 15 + 2 * 20;// max record size
return recordsize;
}
}


static void addrecord(){


Student stu=new Student();
String con = "y";
while (con != "n")
{

Console.Write("Enter student number:");

stu.stunumber = Console.ReadLine();

Console.Write("Enter student name:");

stu.stuname = Console.ReadLine();
pos+= 1; //update position
writeToFile("D:\\Student.txt", stu, pos, stu.size);
Console.WriteLine("Continue?y/n:");
con=Console.ReadLine();
}




}

static void writeToFile(string filename, Student obj, int pos, int size){

FileStream fout;

BinaryWriter bw;

//create a file stream object

fout = new FileStream(filename, FileMode.Append , FileAccess.Write);

//create a binary writer object
bw = new BinaryWriter(fout);

//set file position where to write data
fout.Position = pos * size;
//write data
bw.Write(obj.stunumber );
bw.Write(obj.stuname );
//close objects
bw.Close();
fout.Close();



}

static void readFromFile(string filename){


FileStream fn;
BinaryReader br;

Student stu=new Student();

int currentrecord=0;


//open file to read data

fn = new FileStream(filename, FileMode.Open , FileAccess.Read);


br = new BinaryReader(fn);

//read next record
int i;
for(i=1; i<=(int)(fn.Length)/stu.size;i++){

currentrecord += 1; //update currentrecord position

fn.Seek(currentrecord * stu.size, 0);

stu.stunumber = br.ReadString().ToString() ;
stu.stuname = br.ReadString().ToString() ;

Console.WriteLine(stu.stunumber +"\t"+stu.stuname );



}



//update pos to the current position

pos = currentrecord;

//close objects
br.Close();
fn.Close();

}


}


}





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