checking files using c#

You can use the System.IO.File.Exists() method to determine whether a file exists or not. See this link for examples of usage in both C# and VB.Net:

http://msdn2.microsoft.com/en-us/library/system.io.file.exists.aspx 

Here's a console app in C# which does what you've specifically asked for:

// requires .NET 2.0 or later

using System;
using System.IO;

class Test
{
    static void Main()
    {
        string filePath = @"c:\myfiles\somefile.txt"; // say        
        string[] lines;

        if (File.Exists(filePath))
        {
           lines = File.ReadAllLines(filePath);
           foreach(string line in lines)
              Console.WriteLine(line);
        }
        else
        {
           lines = new string[2];
           lines[0] = "Hello";
           lines[1] = "From C# Corner";
           File.WriteAllLines(filePath, lines);
        } 
    }

}

In VB.Net, this would be:

' requires .NET 2.0 or later

Imports System
Imports System.IO

Class Test

    Shared Sub Main()
    
        Dim filePath As String = "c:\myfiles\somefile.txt"   ' say        
     
        Dim lines As String()

        If File.Exists(filePath)
       
           lines = File.ReadAllLines(filePath)
           For Each line As String In lines
              Console.WriteLine(line)
           Next
 
        Else
       
           lines = New String(2){}
           lines(0) = "Hello"
           lines(1) = "From C# Corner"
           File.WriteAllLines(filePath, lines)

        End If 

   End Sub

End Class