File Input/Output

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So far we haven’t talked about writing words or sentences to a hard drive or reading from it. This part will guide you through those processes. File streams can be stored in plain text and binary format. There are two types of file streams—sequential-access file and random-access file.

Sequential-Access File
In sequential-access file, you can write data to the file or read data from it sequentially from the beginning of the file to the end and vice versa.

Writing to a sequential-access file
Example:
Imports System.IO 'Don’t forget to import IO package
Module Module1

    Sub Main()
        Dim SF As New SequentialFile
        SF.writingToFile("D:\sequentialfile.txt")
        'Note: In this part, we introduce error handling with try..catch..end try block
    End Sub

    Class SequentialFile
        Public Sub writingToFile(ByVal filename As String)
            'Open file for writing
            Dim fout As New FileStream(filename, FileMode.OpenOrCreate, FileAccess.Write)
            'Create StreamWriter tool
            Dim fw As New StreamWriter(fout)
            'write text to file
            fw.WriteLine("Hello World")
            'close file
            fout.Close()
            fw.Close()
        End Sub
    End Class


End Module

Reading from a sequential-access file
Example:
Imports System.IO 'Don’t forget to import IO package
Module Module1

    Sub Main()
        Dim SF As New SequentialFile
      
  'reading from file
        SF.readingFromFile("D:\sequentialfile.txt")
        'Note: In this part, we introduce error handling with try..catch..end try block

    End Sub

    Class SequentialFile
      
Public Sub readingFromFile(ByVal filename As String)
            Dim fn As FileStream
            Dim fr As StreamReader
            Try
                 'Open file for reading
                fn = New FileStream(filename, FileMode.Open, FileAccess.Read)
                 'Create reader tool
                fr = New StreamReader(fn)
                 'Read the content of file
                Dim filecontent As String = fr.ReadToEnd
                Console.WriteLine(filecontent)
                Console.ReadLine()
            Catch e As IOException
                MsgBox(e.Message)
            End Try
            'Close file
            fr.Close()
            fn.Close()
        End Sub
    End Class


End Module