SUMMARY
This step-by-step article shows you how to do six basic file input/output (I/O) operations in Microsoft Visual Basic 2005 or in Microsoft Visual Basic .NET. If you are new to .NET, you will find that the object model for file operations in .NET is similar to the FileSystemObject (FSO) that is popular with many Visual Studio 6.0 developers. To make the transition easier, the functionality that is demonstrated in this article is based on the following Microsoft Knowledge Base article:
186118 (http://support.microsoft.com/kb/186118/) How to use FileSystemObject with Visual Basic
You can still use the FileSystemObject in .NET. Because the FileSystemObject is a Component Object Model (COM) component, .NET requires that access to the object be through the Interop layer. .NET generates a wrapper for the component for you if you want to use it. However, the File, FileInfo, Directory, DirectoryInfo classes, and other related classes in the .NET Framework, offer functionality that is not available with the FSO, without the overhead of the Interop layer.
Requirements
The following list outlines the recommended hardware, software, network infrastructure, and service packs that you need: • Microsoft Windows Server 2003, Microsoft Windows 2000 Professional, Windows 2000 Server, Windows 2000 Advanced Server, or Microsoft Windows NT 4.0 Server
• Microsoft Visual Studio 2005 or Microsoft Visual Studio .NET
• Microsoft Visual Studio 2005 Software Development Kit (SDK) Quickstarts or Microsoft Visual Studio .NET SDK Quickstarts
Step-by-step example
1. In Visual Basic 2005 or in Visual Basic .NET, create a new Windows Application. By default, Form1 is created.
2. Open the code window for Form1.
3. Delete all of the code in the Code-Behind Editor.
4. Paste the following sample code into the Code-Behind Editor window.Option Strict On
Imports System.IO
Public Class Form1
Inherits System.Windows.Forms.Form
Private winDir As String
#Region " Windows Form Designer generated code "
Public Sub New()
MyBase.New()
'Windows Form Designer requires this call.
InitializeComponent()
'Add any initialization after the InitializeComponent() call.
End Sub
'Form overrides dispose to clean up the component list.
Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
If disposing Then
If Not (components Is Nothing) Then
components.Dispose()
End If
End If
MyBase.Dispose(disposing)
End Sub
Friend WithEvents ListBox1 As System.Windows.Forms.ListBox
Friend WithEvents Button3 As System.Windows.Forms.Button
Friend WithEvents Button5 As System.Windows.Forms.Button
Friend WithEvents Button4 As System.Windows.Forms.Button
Friend WithEvents Button2 As System.Windows.Forms.Button
Friend WithEvents Button1 As System.Windows.Forms.Button
Friend WithEvents Button6 As System.Windows.Forms.Button
'Windows Form Designer requires this call.
Private components As System.ComponentModel.Container
'NOTE: Windows Form Designer requires the following procedure.
'You can use the Windows Form Designer to modify it; however, do not
'use the Code Editor to modify it.
Me.Button2 = New System.Windows.Forms.Button()
Me.Button3 = New System.Windows.Forms.Button()
Me.ListBox1 = New System.Windows.Forms.ListBox()
Me.Button4 = New System.Windows.Forms.Button()
Me.Button5 = New System.Windows.Forms.Button()
Me.Button1 = New System.Windows.Forms.Button()
Me.Button6 = New System.Windows.Forms.Button()
Me.SuspendLayout()
'
'Button2
'
Me.Button2.Location = New System.Drawing.Point(272, 64)
Me.Button2.Name = "Button2"
Me.Button2.Size = New System.Drawing.Size(136, 23)
Me.Button2.TabIndex = 1
Me.Button2.Text = "Button2"
'
'Button3
'
Me.Button3.Location = New System.Drawing.Point(272, 96)
Me.Button3.Name = "Button3"
Me.Button3.Size = New System.Drawing.Size(136, 23)
Me.Button3.TabIndex = 2
Me.Button3.Text = "Button3"
'
'ListBox1
'
Me.ListBox1.Location = New System.Drawing.Point(16, 16)
Me.ListBox1.Name = "ListBox1"
Me.ListBox1.Size = New System.Drawing.Size(240, 238)
Me.ListBox1.TabIndex = 5
'
'Button4
'
Me.Button4.Location = New System.Drawing.Point(272, 128)
Me.Button4.Name = "Button4"
Me.Button4.Size = New System.Drawing.Size(136, 23)
Me.Button4.TabIndex = 3
Me.Button4.Text = "Button4"
'
'Button5
'
Me.Button5.Location = New System.Drawing.Point(272, 160)
Me.Button5.Name = "Button5"
Me.Button5.Size = New System.Drawing.Size(136, 23)
Me.Button5.TabIndex = 4
Me.Button5.Text = "Button5"
'
'Button1
'
Me.Button1.Location = New System.Drawing.Point(272, 32)
Me.Button1.Name = "Button1"
Me.Button1.Size = New System.Drawing.Size(136, 23)
Me.Button1.TabIndex = 0
Me.Button1.Text = "Button1"
'
'Button6
'
Me.Button6.Location = New System.Drawing.Point(272, 192)
Me.Button6.Name = "Button6"
Me.Button6.Size = New System.Drawing.Size(136, 23)
Me.Button6.TabIndex = 6
Me.Button6.Text = "Button6"
'
'Form1
'
Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
Me.ClientSize = New System.Drawing.Size(416, 341)
Me.Controls.AddRange(New System.Windows.Forms.Control() _
{Me.Button6, Me.ListBox1, Me.Button5, Me.Button4, _
Me.Button3, Me.Button2, Me.Button1})
Me.Name = "Form1"
Me.Text = "Form1"
Me.ResumeLayout(False)
End Sub
#End Region
Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) _
Handles MyBase.Load
Me.Button1.Text = "Read Text File"
Me.Button2.Text = "Write Text File"
Me.Button3.Text = "View File Information"
Me.Button4.Text = "List Drives"
Me.Button5.Text = "List Subfolders"
Me.Button6.Text = "List Files"
winDir = System.Environment.GetEnvironmentVariable("windir")
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) _
Handles Button1.Click
'Demonstrates how to read a file by using StreamReader
'Uses System.ini as an example
'try...catch is used to detect a 0 byte file.
Dim reader As StreamReader = _
New StreamReader(winDir & "\system.ini")
Try
Me.ListBox1.Items.Clear()
Do 'Until reader.Peek = -1
Me.ListBox1.Items.Add(reader.ReadLine)
Loop Until reader.Peek = -1
Catch
Me.ListBox1.Items.Add("File is empty")
Finally
reader.Close()
End Try
End Sub
Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) _
Handles Button4.Click
'Demonstrates how to obtain a list of disk drives
Dim dirInfo As Directory
Dim drive As String
Me.ListBox1.Items.Clear()
Dim drives() As String = dirInfo.GetLogicalDrives()
For Each drive In drives
Me.ListBox1.Items.Add(drive)
Next
End Sub
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) _
Handles Button3.Click
'Demonstrates how to access file properties. You can access folder properties
'in the same way. More properties are available through the FileInfo class
'than are demonstrated here.
'You can also use the Directory class to obtain this information.
Dim FileProps As FileInfo = New FileInfo(winDir & "\notepad.exe")
With Me.ListBox1.Items
.Clear()
.Add("File Name = " & FileProps.FullName)
.Add("Creation Time = " & FileProps.CreationTime)
.Add("Last Access Time = " & FileProps.LastAccessTime)
.Add("Last Write TIme = " & FileProps.LastWriteTime)
.Add("Size = " & FileProps.Length)
End With
FileProps = Nothing
End Sub
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) _
Handles Button2.Click
'Demonstrates how to create and write to a text file
Dim writer As StreamWriter = _
New StreamWriter("c:\KBTest.txt")
writer.WriteLine("File created using StreamWriter class.")
writer.Close()
Me.ListBox1.Items.Clear()
Me.ListBox1.Items.Add("File Written to C:\KBTest.txt")
End Sub
Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) _
Handles Button5.Click
'Demonstrates how to get a list of folders (example uses Windows folder)
Dim dir As String
Me.ListBox1.Items.Clear()
Dim dirs() As String = Directory.GetDirectories(winDir)
For Each dir In dirs
Me.ListBox1.Items.Add(dir)
Next
End Sub
Private Sub Button6_Click(ByVal sender As Object, ByVal e As System.EventArgs) _
Handles Button6.Click
'Demonstrates how to get a list of files (example uses Windows folder)
Dim file As String
Me.ListBox1.Items.Clear()
Dim files() As String = Directory.GetFiles(winDir)
For Each file In files
Me.ListBox1.Items.Add(file)
Next
End Sub
End Class
Note You must change the code in Visual Basic 2005. By default, Visual Basic creates two files for the project when you create a Windows Forms project. If the form is named Form1, the two files that represent the form are named Form1.vb and Form1.Designer.vb. You write the code in the Form1.vb file. The Windows Forms Designer writes the code in the Form1.Designer.vb file. The Windows Forms Designer uses the partial keyword to divide the implementation of Form1 into two separate files. This behavior prevents the designer-generated code from being interspersed with your code.
For more information about the new Visual Basic 2005 language enhancements, visit the following Microsoft Developer Network (MSDN) Web site:
source: http://msdn2.microsoft.com/en-us/library/ms379584(vs.80).aspx
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