VB.Net Tutorial/Stream File/StreamReader

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Check Exception in file reading

<source lang="vbnet">Imports System.IO Imports System public class Test

  public Shared Sub Main
       Dim sr As IO.StreamReader
       Try
           sr = New IO.StreamReader("test.txt")
           Console.WriteLine(sr.ReadToEnd())
       Catch ex As IO.FileNotFoundException
           Console.WriteLine("FileNotFoundException")
       Catch ex As IO.IOException
           Console.WriteLine("IOException")
       Catch ex As Exception
           Console.WriteLine("Error Loading File")
       Finally
           sr.Close()
       End Try
  End Sub

End class</source>

Hello world!

Create StreamReader from FileStream

<source lang="vbnet">Imports System.IO

Public Class Tester

   Public Shared Sub Main
       Dim f As System.IO.FileStream
       Dim r As System.IO.StreamReader
       Dim mylength As Integer
       Dim i As Integer
       f = New System.IO.FileStream("test.txt", IO.FileMode.Open, IO.FileAccess.Read)
       r = New System.IO.StreamReader(f)
       Console.WriteLine(r.ReadToEnd())
       f.Close()
       r.Close()
   End Sub

End Class</source>

Read all text in a text file by using StreamReader

<source lang="vbnet">Imports System.IO Module Module1

   Sub Main()
       Dim SourceFile As StreamReader
       Try
           SourceFile = New StreamReader("test.txt")
           Console.WriteLine(SourceFile.ReadToEnd())
           SourceFile.Close()
       Catch Except As Exception
           Console.WriteLine("Debug file does not yet exist")
       End Try
   End Sub

End Module</source>

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...

Read text file to a char array

<source lang="vbnet">Imports System.IO

Public Class Tester

   Public Shared Sub Main
       Dim f As System.IO.FileStream
       Dim r As System.IO.StreamReader
       Dim mylength As Integer
       Dim i As Integer
       Dim mybuffer(100) As Char
       f = New System.IO.FileStream("test.txt", IO.FileMode.Open, IO.FileAccess.Read)
       r = New System.IO.StreamReader(f)
       r.Read(mybuffer, 0, 100)
       Console.WriteLine(mybuffer)
       f.Close()
       r.Close()
   End Sub

End Class</source>

Read text file to the end

<source lang="vbnet">Imports System.IO Public Class Tester

   Public Shared Sub Main
   
           Try
              Dim stream As StreamReader
              stream = New StreamReader("test.vb")
              Console.WriteLine(stream.ReadToEnd())
           Catch exceptionCatch As IOException
              Console.WriteLine("FILE ERROR")
           End Try
   End Sub

End Class</source>

StreamReader: Peek

<source lang="vbnet">Imports System.IO Public Class Tester

   Public Shared Sub Main
       Dim fsStream As New FileStream("test.txt", FileMode.Open, FileAccess.Read)
       Dim srReader As New StreamReader(fsStream)
       Try
           srReader.BaseStream.Seek(0, SeekOrigin.Begin)
           While srReader.Peek() > -1
               Console.WriteLine(srReader.ReadLine())
           End While
           srReader.Close()
       Catch ex As IOException
           Console.WriteLine(ex.Message)
       End Try
   End Sub

End Class</source>

StreamReader: read to a buffer

<source lang="vbnet">Imports System.IO

Public Class Tester

   Public Shared Sub Main
       Dim f As System.IO.FileStream
       Dim r As System.IO.StreamReader
       Dim mylength As Integer
       Dim i As Integer
       Dim mybuffer(100) As Char
       f = New System.IO.FileStream("test.txt", IO.FileMode.Open, IO.FileAccess.Read)
       r = New System.IO.StreamReader(f)
       r.Read(mybuffer, 0, 100)
       Console.WriteLine(mybuffer)
       f.Close()
       r.Close()
   End Sub

End Class</source>

Use Finally clause to close a stream

<source lang="vbnet">Imports System.IO Imports System.Windows.Forms Module Module1

   Sub Main()
       Dim FileDB As New OpenFileDialog()
       FileDB.Filter = "All files | *.* | Text files | *.txt"
       FileDB.FilterIndex = 2
       FileDB.InitialDirectory = "C:\Temp"
       FileDB.AddExtension = True
       FileDB.DefaultExt = "txt"
       If (FileDB.ShowDialog() = DialogResult.OK) Then
           Dim SourceFile As StreamReader
           SourceFile = New StreamReader(FileDB.FileName)
           If (Not SourceFile Is Nothing) Then
               Try
                   Console.WriteLine(SourceFile.ReadToEnd())
               Catch Except As Exception
                   Console.WriteLine("Error: " & Except.Message)
               Finally
                   Console.WriteLine("In finally statements")
                   SourceFile.Close()
               End Try
           End If
       Else
           Console.WriteLine("User selected Cancel")
       End If
   End Sub

End Module</source>