File I/O in C#

File is the collection of data that is stored in a disk with specific name, when we open a file for read or write the data it becomes a steam.

The steam is the sequence of the byte passing through the communication path, there are two types of steam input steam and output steam.

Input steam – Input steam is used to read the data from the file.

Output steam – Output steam is used to write the data into file.

C# I/O Classes – In C# system.IO name space is used to performing operation with file.System.IO name space contains following classes.

BinaryReader – Used to read the primitive data from binary steam

Binarywriter – Used to write the primitive data in binary format.

Directory – Used to manipulating a directory structurer.

DirectoryInfo – Used to perform operation on directories.

DriveInfo – It gives the information for the drives.

File – Used for manipulating files.

FileInfo – It is used to perform operation on file.

Filesteam – Used to read and write from the file.

Path – Perform operation on path information.

SteamReader – It is used to read character from a byte steam.

Steamwriter – It is used to writing character to a steam.

StringReader – Used to read from string buffer.

StringWriter – Used to write into a string buffer.

Example – the following program is used for Filesteam class - 

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

namespace ConsoleApplication19
{
    class Program
    {
        FileStream FS = new FileStream("test.dat", FileMode.OpenOrCreate, FileAccess.ReadWrite);

         for (int i = 1; i<= 20; i++)
         {
            FS.WriteByte((byte)i);
         }
        
         FS.Position = 0;
         for (int i = 0; i <= 20; i++)
         {
            Console.Write(F.ReadByte() + " ");
         }
         FS.Close();
         Console.ReadKey();
      }
}

Output - 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 -1

                                                             Author - Sachin Pathak

What is array in C#

An array store fixed-size sequential collection of elements of the same datatype. It is used to store the collection of data of same data type at contiguous memory locations.

Declaration of array –

Datatype [ ] arrayname;

Datatype specify the data of elements in the array.

[ ] specify the size of the array.

And arrayname is the name of array.

Initializing an Array -

An array is the reference type so we need new keyword to create the instance of the array. For example –

double d= new double [10];

Assigning value to an Array –

We can assign the value to an array by using the index number. For example –

double d= new double [10];

d[0]=100;

we can also assign the value to an array at the time of declaration –

double[ ] d={10,15,20,25,30}

We can also create and initialize the array as the following ways

int[ ] mark=new int[5] {20,21,22,23,29}

or

int[] mark=new int[ ] {22,24,26,28,29}

The Example of the array is given below:

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

namespace ConsoleApplication18
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] n = new int[10];
            int i, j;
            for (i = 0; i < 10; i++)
            {
                n[i] = i + 10;
            }
            for (j = 0; j < 10; j++)
            {
                Console.WriteLine("index[{0}] = {1}", j, n[j]);
            }
            Console.ReadKey();
        }
    }
}
 

Output - 

Following are the some important concept related to the array.

Multi-dimensional arrays – C# support multi-dimensional arrays. It is also called two dimensional arrays.

Jagged arrays – The array of array is also jagged arrays.

Passing arrays to functions – We can pass a function to an array by specifying the array name without an index.

Param arrays – Param arrays is used to pass unknown number of parameter to a function

The array class – The array class provides the various properties and methods by define system name space.

SQL Select Top Clause

The SQL select top clause is used to return the number of records. It is very helpful when we want to fetch the record from a very large table that contains thousands of records.

Example –

Firstly we create a table with name “emp”-

 Select top 2 * from emp

Output - 

SQL Select TOP PERCENT Example -

Select top 50 percent * from emp

Output -