Programming Microsoft Visual Basic .NET/Programming Microsoft Visual Basic .NET (Microsoft Press)(X08-78517)(2002).bin/setup/vbnet/10 directories, files, and streams/dirfiledemo/module1.vb

Text File | 2002-03-20 | 17.0 KB | 445 lines

Imports System.Globalization
Imports System.IO
Imports Microsoft.Win32

Module MainModule

    Sub Main()
        ' Run one of the Textxxxx procedures below by uncommenting only one statement

        'TestFileDirectory()
        'TestFileDirectoryInfo()
        'TestPath()
        'TestStreamReader()
        'TestStreamWriter()
        'TestBinaryReaderWriter()
        'TestMemoryStream()
        'TestStringReaderWriter()
        'TestCustomBinaryReaderWriter()

        ' These statements are usuful when running inside Visual Studio.NET
        Console.WriteLine("")
        Console.WriteLine(">>> Press Enter to terminate the program <<<")
        Console.ReadLine()
    End Sub

    ' this procedure tests the File and Directory objects

    Sub TestFileDirectory()
        ' Save the current directory.
        Dim currDir As String = Directory.GetCurrentDirectory
        ' Change the current directory to something else.
        Directory.SetCurrentDirectory("C:\")
        ' check that it worked
        Console.WriteLine("Current directory: " & Directory.GetCurrentDirectory)
        ' Restore the current directory.
        Directory.SetCurrentDirectory(currDir)

        ' Retrieve all the root paths.
        Dim strRoots() As String = Directory.GetLogicalDrives
        Dim s As String
        For Each s In strRoots
            Console.WriteLine(s)         ' => C:\  D:\  ...
        Next

        ' display files and directories in C:\DOCS
        PrintDirTree("c:\docs", True)

        ' Display all the *.txt files in C:\DOCS.
        Dim fname As String
        For Each fname In Directory.GetFiles("c:\docs", "*.txt")
            Console.WriteLine(fname)
        Next
        Console.WriteLine("")

        ' Display system and hidden files in C:\.
        For Each fname In Directory.GetFiles("C:\")
            Dim attr As FileAttributes = File.GetAttributes(fname)
            ' Show the file if it is marked as either hidden or system (or both).
            If CBool(attr And FileAttributes.Hidden) Or CBool(attr And FileAttributes.System) Then
                ' NOTE: you can make the IF condition more concise as follows:
                'If CBool(attr And (FileAttributes.Hidden Or FileAttributes.System)) Then
                Console.WriteLine(fname)
            End If
        Next

        ' ensure that we aren't destroying an existing directory tree
        If Not Directory.Exists("c:\myapp") Then
            ' Next line works even if the C:\MyApp directory doesn't exist yet.
            Directory.CreateDirectory("C:\MyApp\Data")
            ' check that it worked
            If Directory.Exists("c:\myapp\data") Then
                Console.WriteLine("The C:\MYAPP\DATA directory has been created.")
            End If
            ' delete it, forcing deletion of inner directories
            Directory.Delete("c:\MyApp", True)
        End If

        ' Change the access date-time of all files in C:\DOCS.
        For Each fname In Directory.GetFiles("c:\docs", "*.txt")
            File.SetLastAccessTime(fname, Date.Now)
        Next

        ' a "touch" utility
        ' NOTE: test by running from command prompt and passing one more more file names
        For Each fname In Environment.GetCommandLineArgs
            File.SetCreationTime(fname, Date.Now)
        Next
    End Sub

    ' traverse a directory tree

    Sub PrintDirTree(ByVal dir As String, ByVal showFiles As Boolean, _
    Optional ByVal level As Integer = 0)
        Dim subdir As String
        Dim fname As String

        ' Display the name of this directory with correct indentation.
        Console.WriteLine(New String("-"c, level * 2) & dir)

        Try
            ' Display all files in this directory, with correct indentation.
            If showFiles Then
                For Each fname In Directory.GetFiles(dir)
                    Console.WriteLine(New String(" "c, level * 2 + 2) & fname)
                Next
            End If
            ' A recursive call for all the subdirectories in this directory.
            For Each subdir In Directory.GetDirectories(dir)
                PrintDirTree(subdir, showFiles, level + 1)
            Next
        Catch
            ' Do nothing if any error (presumably "Drive not ready").
        End Try
    End Sub

    ' test DirectoryInfo or FileInfo classes

    Sub TestFileDirectoryInfo()
        ' Create a DirectoryInfo object that points to C:\.
        Dim rootDi As New DirectoryInfo("C:\")
        ' Create a FileInfo object that points to C:\Autoexec.bat.
        Dim fi As New FileInfo("C:\Autoexec.bat")

        ' List the directories in C:\.
        Dim di As DirectoryInfo
        For Each di In rootDi.GetDirectories
            Console.WriteLine(di.Name)
        Next
        Console.WriteLine("")

        ' List all the *.txt files in C:\.
        For Each fi In rootDi.GetFiles("*.txt")
            Console.WriteLine(fi.Name)
        Next
        Console.WriteLine("")

        Dim fsi As FileSystemInfo

        ' Display all files and subdirectories in C:\
        ' Note that we can create the DirectoryInfo object on-the-fly.
        For Each fsi In (New DirectoryInfo("C:\")).GetFileSystemInfos
            ' Use a [dir] or [file] prefix.
            If CBool(fsi.Attributes And FileAttributes.Directory) Then
                Console.Write("[dir] ")
            Else
                Console.Write("[file] ")
            End If
            ' Print name and creation date
            Console.WriteLine(fsi.Name & " - " & fsi.CreationTime)
        Next
    End Sub

    ' this procedure tests the Path class

    Sub TestPath()
        Console.WriteLine(Path.AltDirectorySeparatorChar)  ' => /
        Console.WriteLine(Path.DirectorySeparatorChar)     ' => \
        Console.WriteLine(Path.InvalidPathChars)           ' => "<>|
        Console.WriteLine(Path.PathSeparator)              ' => ;
        Console.WriteLine(Path.VolumeSeparatorChar)        ' => :

        ' Note that paths are in 8.3 MsDos format.
        Console.WriteLine(Path.GetTempPath)
        ' => C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\
        Console.WriteLine(Path.GetTempFileName)
        ' => C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\tmp1B2.tmp

        Dim fil As String = "C:\MyApp\Bin\MyApp.exe"
        Console.WriteLine(Path.GetDirectoryName(fil))            ' => C:\MyApp\Bin
        Console.WriteLine(Path.GetFileName(fil))                 ' => MyApp.exe
        Console.WriteLine(Path.GetExtension(fil))                ' => .exe
        Console.WriteLine(Path.GetFileNameWithoutExtension(fil)) ' => MyApp
        Console.WriteLine(Path.GetPathRoot(fil))                 ' => C:\
        Console.WriteLine(Path.HasExtension(fil))                ' => True
        Console.WriteLine(Path.IsPathRooted(fil))                ' => True

        ' Next line assumes that current directory is C:\MyApp.
        Console.WriteLine(Path.GetFullPath("MyApp.Exe"))   ' => C:\MyApp\MyApp.Exe

        Console.WriteLine(Path.ChangeExtension("MyApp.Exe", "Dat"))  ' => MyApp.Dat

        Console.WriteLine(Path.Combine("C:\MyApp\", "MyApp.Dat"))
        ' => C:\MyApp\MyApp.Dat
    End Sub

    ' this procedure tests StreamReader objects

    Sub TestStreamReader()
        ' The File.OpenText shared method.
        Dim sr As StreamReader = File.OpenText("c:\autoexec.bat")

        ' the following block of code include alternative
        ' open tecniques , as described in the book

#If False Then
        ' The OpenText instance method of a FileInfo object.
        Dim fi2 As New FileInfo("c:\autoexec.bat")
        Dim sr2 As StreamReader = fi2.OpenText

        ' By passing a FileStream from the Open method of File class to
        ' the StreamReader's constructor method.
        ' (This technique lets you specify mode, access, and share mode.)
        Dim st3 As Stream = File.Open("C:\autoexec.bat", _
            FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite)
        Dim sr3 As New StreamReader(st3)

        ' By opening a FileStream on the file, and then passing it
        ' to the StreamReader's constructor method.
        Dim fs4 As New FileStream("C:\autoexec.bat", FileMode.Open)
        Dim sr4 As New StreamReader(fs4)

        ' By getting a FileStream from the OpenRead method of File class
        ' and passing it to the StreamReader's constructor.
        Dim sr5 As New StreamReader(File.OpenRead("c:\autoexec.bat"))

        ' By passing the file name to the StreamReader's constructor.
        Dim sr6 As New StreamReader("c:\autoexec.bat")

        ' By passing the file name and encoding.
        Dim sr7 As New StreamReader("c:\autoexec.bat", System.Text.Encoding.Unicode)
        Dim sr8 As New StreamReader("c:\autoexec.bat", System.Text.Encoding.ASCII)
        ' As before, but we let the system decide the best encoding.
        Dim sr9 As New StreamReader("c:\autoexec.bat", True)
#End If

        ' Display all the text lines in the file.
        Do Until sr.Peek = -1
            ' The ReadLine methods reads whole lines.
            Console.WriteLine(sr.ReadLine)
        Loop
        ' Always close a StreamReader when you've done with it.
        sr.Close()

        ' Read the entire contents of C:\Autoexec.bat in one shot.
        sr = New StreamReader("c:\autoexec.bat")
        Dim fileContents As String = sr.ReadToEnd()
        Console.WriteLine(fileContents)
        Console.WriteLine("")

        ' If the file contains "WARNING" then process it again, one character at a
        ' time (admittedly a silly thing to do, but it's just a demo).
        If fileContents.Length >= 10 Then
            ' Reset the stream's pointer to the beginning.
            sr.BaseStream.Seek(0, SeekOrigin.Begin)
            ' Read individual characters until EOF is reached.
            Do Until sr.Peek() = -1
                ' Read returns an integer, convert it to Char.
                Console.Write(sr.Read.ToString)
            Loop
        End If
        sr.Close()
        Console.WriteLine("")
    End Sub

    ' this procedure tests StreamWriter objects

    Sub TestStreamWriter()

        ' skip over alternative open tecniques in this demo
#If False Then
        ' The File class's CreateText or AppendText methods (shared or instance).
        Dim sw1 As StreamWriter = File.CreateText("c:\temp.dat")

        ' By passing a FileStream from the Open method of File class to
        ' the StreamWriter's constructor method.
        Dim st2 As Stream = File.Open("C:\temp.dat", _
            FileMode.Create, FileAccess.ReadWrite, FileShare.None)
        Dim sw2 As New StreamWriter(st2)

        ' By opening a FileStream on the file, and then passing it
        ' to the StreamWriter's constructor method.
        Dim fs3 As New FileStream("C:\autoexec.bat", FileMode.Open)
        Dim sw3 As New StreamWriter(fs3)

        ' By getting a FileStream from the OpenWrite method of File class
        ' and passing it to the StreamWriter's constructor.
        Dim sw4 As New StreamWriter(File.OpenWrite("C:\temp.dat"))

        ' By passing the file name to the StreamWriter's constructor.
        Dim sw5 As New StreamWriter("C:\temp.dat")
#End If

        ' Copy C:\Autoexec.bat to C:\Autoexec.new, and covert chars to uppercase.
        Dim sr As New StreamReader("C:\Autoexec.bat")
        Dim sw As New StreamWriter("C:\Autoexec.new")

        Do Until sr.Peek = -1
            ' The ReadLine method returns a string, so we can
            ' convert it to uppercase on the fly.
            sw.WriteLine(sr.ReadLine.ToUpper)
        Loop
        sr.Close()
        sw.Close()      ' This actually writes data to file and closes it.

        ' do it again in one operation
        sr = New StreamReader("C:\Autoexec.bat")
        sw = New StreamWriter("C:\Autoexec.new")
        sw.Write(sr.ReadToEnd.ToUpper)
        sr.Close()
        sw.Close()
    End Sub

    ' this procedure tests the BinaryReader and BinaryWriter classes

    Sub TestBinaryReaderWriter()
        ' Associate a stream to a new file, opened with write access.
        Dim st As Stream = File.Open("c:\values.dat", FileMode.Create, FileAccess.Write)
        ' Create a BinaryWriter associated to the output stream.
        Dim bw As New BinaryWriter(st)

        Dim i As Integer, rand As New Random()
        For i = 1 To 10
            bw.Write(rand.NextDouble)
        Next
        ' Flush the output data to the file.
        bw.Close()
        st.Close()

        ' Read back values written in previous example.

        ' Associate a stream to an existing file, opened with read access.
        Dim st2 As Stream = File.Open("c:\values.dat", FileMode.Open, FileAccess.Read)
        ' Create a BinaryReader associated to the input stream.
        Dim br2 As New BinaryReader(st2)

        ' Loop until there is data avaialble.
        Do Until br2.PeekChar = -1
            ' Read the next element.
            Console.WriteLine(br2.ReadDouble)
        Loop
        br2.Close()
        st2.Close()
    End Sub

    ' this procedure tests the MemoryStream object

    Sub TestMemoryStream()
        ' Create a memory stream with initial capacity of 1K.
        Dim st As New MemoryStream(1024)
        Dim bw As New BinaryWriter(st)
        Dim i As Integer, rand As New Random()
        ' Write 10 random Double values to the stream.
        For i = 1 To 10
            bw.Write(rand.NextDouble)
        Next

        ' Rewind the stream to the beginning.
        st.Seek(0, SeekOrigin.Begin)
        Dim br As New BinaryReader(st)

        Do Until br.PeekChar = -1
            Console.WriteLine(br.ReadDouble)
        Loop
        br.Close()
        st.Close()

        ' Write two strings to a MemoryStream.
        st = New MemoryStream(1000)
        bw = New BinaryWriter(st)
        bw.Write("length-prefixed string")

        ' we'll use for both reading and writing
        Dim buffer(1024) As Char                    'a 1K buffer

        Dim s As String = "13 Characters"           ' fixed-length string
        s.CopyTo(0, buffer, 0, 13)                  ' copy into the buffer
        bw.Write(buffer, 0, 13)                     ' output first 13 chars in buffer
        bw.Write(buffer, 0, 13)                     ' do it twice

        ' Rewind the stream, and prepare to read from it.
        st.Seek(0, SeekOrigin.Begin)
        br = New BinaryReader(st)
        ' Reading the length-prefixed string is easy.
        Console.WriteLine(br.ReadString)            ' => length-prefixed string

        ' Read the fixed-length string into the buffer
        br.Read(buffer, 0, 13)                      ' Read 13 characters.
        s = New String(buffer, 0, 13)               ' convert to a string
        Console.WriteLine(s)                        ' => 13 Characters

        ' Another way to read a fixed-length string
        s = New String(br.ReadChars(13))
        Console.WriteLine(s)                        ' => 13 Characters
    End Sub

    ' this procedure tests StringReader and StringWriter classes

    Sub TestStringReaderWriter()
        Dim veryLongString As String
        ' initialize this variable with the contents of Autoexec.bat
        Dim sr As New StreamReader("c:\autoexec.bat")
        veryLongString = sr.ReadToEnd
        sr.Close()

        ' The veryLongString variable contains the text to parse.
        Dim strReader As New StringReader(veryLongString)
        ' Display individual lines of text.
        Do Until strReader.Peek = -1
            Console.WriteLine(strReader.ReadLine)
        Loop

        ' Create a string with the space-separated abbreviated names of weekdays.
        ' A StringBuilder of 7*4 characters is enough.
        Dim sb As New System.Text.StringBuilder(28)
        ' The StringWriter associated to the StringBuilder.
        Dim strWriter As New StringWriter(sb)

        ' Output day names to the string.
        Dim d As String
        For Each d In DateTimeFormatInfo.CurrentInfo.AbbreviatedDayNames
            strWriter.Write(d)
            strWriter.Write(" ")        ' Append a space.
        Next
        Console.WriteLine(sb)           ' => Sun Mon Tue Wed Thu Fri Sat
    End Sub

    ' this procedure tests custom BinaryReaderEx and BinaryWriterEx classes

    Sub TestCustomBinaryReaderWriter()
        Dim st As New MemoryStream(1000)
        Dim bw As New BinaryWriterEx(st)

        ' Write a Person object, then a û1 value (short).
        Dim p As New Person("Joe", "Doe")
        bw.Write(p)
        bw.Write(-1S)

        ' Rewind the stream, and prepare to read from it.
        st.Seek(0, SeekOrigin.Begin)
        Dim br As New BinaryReaderEx(st)

        ' Read a Person object, and prove that properties have been preserved.
        Dim p2 As Person = br.ReadPerson()
        Console.WriteLine(p.FirstName & " " & p.LastName)
        ' Read the Short value.
        Console.WriteLine(br.ReadInt16)

        ' Clean up
        bw.Close()
        br.Close()
        st.Close()
    End Sub

End Module