15 文件、目录和流
15.1 Path
代码
Imports
System.IO
Public
Class
Class1
Sub
TestPathType()
Console.WriteLine(Path.AltDirectorySeparatorChar)
'
=> /
Console.WriteLine(Path.DirectorySeparatorChar)
'
=> \
Console.WriteLine(Path.PathSeparator)
'
=> ;
Console.WriteLine(Path.VolumeSeparatorChar)
'
=> :
'
Note: the actual output from following methods includes unprintable characters.
Console.WriteLine(Path.GetInvalidPathChars())
'
=> <>|
Console.WriteLine(Path.GetInvalidFileNameChars())
'
=> <>|:*?\/
Console.WriteLine(Path.GetTempPath)
'
=> C:\Documents and Settings\Francesco\Local Settings\Temp
Console.WriteLine(Path.GetTempFileName)
'
=> C:\Documents and Settings\Francesco\Local Settings\Temp\tmp1FC7.tmp
'
从路径字符串中提取信息
Dim
file
As
String
=
"
C:\MyApp\Bin\MyApp.exe
"
Console.WriteLine(Path.GetDirectoryName(file))
'
=> C:\MyApp\Bin
Console.WriteLine(Path.GetFileName(file))
'
=> MyApp.exe
Console.WriteLine(Path.GetExtension(file))
'
=> .exe
Console.WriteLine(Path.GetFileNameWithoutExtension(file))
'
=> MyApp
Console.WriteLine(Path.GetPathRoot(file))
'
=> C:\
Console.WriteLine(Path.HasExtension(file))
'
=> True
Console.WriteLine(Path.IsPathRooted(file))
'
=> True
'
Retrieve the Windows main directory (parent of Windows system directory)
Console.WriteLine(Path.GetDirectoryName(Environment.SystemDirectory))
'
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
'
\..表示当前目录的上一级目录
Console.WriteLine(Path.GetFullPath(
"
c:\public\..\private\filename
"
))
End Sub
End Class
15.2 Directory和File
15.2.1 列举目录和文件
代码
Imports
System.IO
Public
Class
Class1
Sub
DisplayDirTree(
ByVal
dir
As
String
,
ByVal
showFiles
As
Boolean
,
Optional
ByVal
level
As
Integer
=
0
)
'
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
=
True
Then
For
Each
fname
As
String
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
As
String
In
Directory.GetDirectories(
dir
)
DisplayDirTree(subdir, showFiles, level
+
1
)
Next
Catch
'
Do nothing if any error (presumably "Drive not ready").
End
Try
End Sub
'
显示系统中所有驱动器的目录树
Sub
a()
For
Each
rootDir
As
String
In
Directory.GetLogicalDrives
DisplayDirTree(rootDir,
True
,
0
)
Next
End Sub
'
Display all the *.txt files in C:\DOCS.
Sub
b()
For
Each
fname
As
String
In
Directory.GetFiles(
"
c:\docs
"
,
"
*.txt
"
)
Console.WriteLine(fname)
Next
End Sub
'
Display only read-only .txt files in the c:\docs folder.
Sub
c()
For
Each
fname
As
String
In
Directory.GetFiles(
"
c:\docs
"
,
"
*.txt
"
)
If
CBool
(File.GetAttributes(fname)
And
FileAttributes.ReadOnly)
Then
Console.WriteLine(fname)
End
If
Next
End Sub
'
自动在子目录中搜索
Sub
d()
For
Each
file
As
String
In
Directory.GetFiles(
"
c:\windows
"
,
"
*.dll
"
, System.IO.SearchOption.AllDirectories)
Console.WriteLine(file)
Next
End Sub
End Class
15.2.2 管理目录和文件
代码
Imports
System.IO
Module
Module2
Sub
a()
Dim
currDir
As
String
=
Directory.GetCurrentDirectory
Directory.SetCurrentDirectory(
"
c:\temp
"
)
''''''''''''
'
'''
'
''''''''''''
'
Directory.SetCurrentDirectory(currDir)
End Sub
Sub
b()
Directory.CreateDirectory(
"
c:\myTemp\data
"
)
End Sub
Sub
c()
If
File.Exists(
"
c:\data.txt
"
)
Then
File.Move(
"
c:\data.txt
"
,
"
d:\data.txt
"
)
End
If
End Sub
Sub
d()
Directory.Delete(
"
c:\tempDir
"
,
True
)
End Sub
'
Display system and hidden files in C:\.
Sub
e()
For
Each
fname
As
String
In
Directory.GetFiles(
"
C:\
"
)
Dim
attr
As
FileAttributes
=
File.GetAttributes(fname)
'
Display the file if marked as hidden or system (or both).
If
CBool
(attr
And
(FileAttributes.Hidden
Or
FileAttributes.System))
Then
Console.WriteLine(fname)
End
If
Next
End Sub
Sub
f()
File.Copy(
"
c:\data.bin
"
,
"
c:\backup\data.bin
"
,
True
)
End Sub
Sub
g()
File.Replace(
"
c:\data.bin
"
,
"
c:\newdata.bin
"
,
"
c:\data.bak
"
,
True
)
End Sub
End Module
15.3 DirectoryInfo和FileInfo
代码
Imports
System.IO
Module
Module3
Sub
a()
'
Create a DirectoryInfo object that points to C:\.
Dim
diRoot
As
New
DirectoryInfo(
"
c:\
"
)
'
Create a FileInfo object that points to c:\autoexec.bat.
Dim
fiAutoexec
As
New
FileInfo(
"
c:\autoexec.bat
"
)
'
List the directories in c:\.
For
Each
di
As
DirectoryInfo
In
diRoot.GetDirectories()
Console.WriteLine(di.Name)
Next
'
List all the *.txt files in c:\.
For
Each
fi
As
FileInfo
In
diRoot.GetFiles(
"
*.txt
"
)
Console.WriteLine(fi.Name)
Next
'
Show files and directories in one operation
For
Each
fsi
As
FileSystemInfo
In
diRoot.GetFileSystemInfos()
'
Use the [dir] or [file] prefix.
Dim
prefix
As
String
=
Nothing
If
CBool
(fsi.Attributes
And
FileAttributes.Directory)
Then
prefix
=
"
dir
"
Else
prefix
=
"
file
"
End
If
'
Print type, name and creation date.
Console.WriteLine(
"
[{0}] {1} ?{2}
"
, prefix, fsi.Name, fsi.CreationTime)
Next
'
List all empty files in c:\.
For
Each
fi
As
FileInfo
In
diRoot.GetFiles()
If
fi.Length
=
0
Then
Console.WriteLine(fi.Name)
Next
End Sub
Sub
b()
'
List all empty files in c:\.
Dim
fiDoc
As
New
FileInfo(
"
c:\temps\temp.txt
"
)
For
Each
fi
As
FileInfo
In
fiDoc.Directory.GetFiles()
Console.WriteLine(fi.Name)
Next
End Sub
'
创建c:\tempdocs\Reports子目录,然后将其删除
Sub
c()
Dim
diDocs
As
New
DirectoryInfo(
"
c:\tempdocs
"
)
diDocs.CreateSubdirectory(
"
Reports
"
)
diDocs.Delete(
True
)
End Sub
'
Encrypt all the writable files in the c:\private directory.
Sub
d()
Dim
diPrivate
As
New
DirectoryInfo(
"
c:\private
"
)
For
Each
fi
As
FileInfo
In
diPrivate.GetFiles()
If
Not
fi.IsReadOnly
Then
fi.Encrypt()
Next
End Sub
End Module
15.4 DriveInfo
代码
Imports
System.IO
Module
Module4
'
Display the volume label of drive C.
Sub
a()
Dim
driveC
As
New
DriveInfo(
"
c:
"
)
Console.WriteLine(
"
Label of C: drive: {0}
"
, driveC.VolumeLabel)
End Sub
'
Display name and total size of all available drives.
Sub
b()
For
Each
di
As
DriveInfo
In
DriveInfo.GetDrives()
If
di.IsReady
Then
Console.WriteLine(
"
Drive {0}: {1:N} bytes
"
, di.Name, di.TotalSize)
End
If
Next
End Sub
Sub
c()
Dim
driveD
As
New
DriveInfo(
"
d:
"
)
driveD.VolumeLabel
=
"
MyData
"
End Sub
'
Display information of all drives
Sub
d()
Console.WriteLine(
"
{0,-6}{1,-10}{2,-8}{3,-16}{4,18}{5,18}
"
,
"
Name
"
,
"
Label
"
,
"
Type
"
,
"
Format
"
,
"
TotalSize
"
,
"
TotalFreeSpace
"
)
Console.WriteLine(
New
String
(
"
-
"
c,
78
))
For
Each
di
As
DriveInfo
In
DriveInfo.GetDrives()
If
di.IsReady
Then
Console.WriteLine(
"
{0,-6}{1,-10}{2,-8}{3,-16}{4,18:N0}{5,18:N0}
"
,
di.Name, di.VolumeLabel, di.DriveType.ToString, di.DriveFormat, di.TotalSize, di.TotalFreeSpace)
Else
Console.WriteLine(
"
{0,-6}(not ready)
"
, di.Name)
End
If
Next
End Sub
End Module
15.7 Stream
15.7.1 流操作
15.7.2流式阅读器和流式编写器
15.7.3读取和写入文本文件
代码
Imports
System.IO
Imports
System.Text
Module
Module5
Dim
fileName
As
String
=
"
c:\test.txt
"
'
With the File.OpenText static method
Sub
a()
Dim
sr
As
StreamReader
=
File.OpenText(fileName)
End Sub
'
With the OpenText instance method of a FileInfo object
Sub
a2()
Dim
fi2
As
New
FileInfo(fileName)
Dim
sr2
As
StreamReader
=
fi2.OpenText
End Sub
'
By passing a FileStream from the Open method of the File class to
'
the StreamReader's constructor method
'
(This technique lets you specify mode, access, and share mode.)
Sub
a3()
Dim
st3
As
Stream
=
File.Open(fileName, FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite)
Dim
sr3
As
New
StreamReader(st3)
End Sub
'
By opening a FileStream on the file and then passing it
'
to the StreamReader's constructor method
Sub
a4()
Dim
fs4
As
New
FileStream(fileName, FileMode.Open)
Dim
sr4
As
New
StreamReader(fs4)
End Sub
'
By getting a FileStream from the OpenRead method of the File class
'
and passing it to the StreamReader's constructor
Sub
a5()
Dim
sr5
As
New
StreamReader(File.OpenRead(fileName))
End Sub
'
By passing the filename to the StreamReader's constructor
Sub
a6()
Dim
sr6
As
New
StreamReader(fileName)
End Sub
'
By passing the filename and encoding
Sub
a7()
Dim
sr7
As
New
StreamReader(
"
c:\autoexec.bat
"
, System.Text.Encoding.Unicode)
Dim
sr8
As
New
StreamReader(fileName, System.Text.Encoding.ASCII)
End Sub
'
As before, but we let the system decide the best encoding.
Sub
a8()
Dim
sr9
As
New
StreamReader(fileName,
True
)
End Sub
'
Create a file for sequential reading and writing, with a 2K buffer;
'
The file will be deleted when closed.
Sub
b()
Dim
fs10
As
New
FileStream(
"
c:\tryme.tmp
"
,
FileMode.CreateNew,
FileAccess.ReadWrite,
FileShare.Read,
2048
,
FileOptions.SequentialScan
Or
FileOptions.DeleteOnClose)
End Sub
'
Display all the text lines in the c:\test.txt file.
Sub
c()
Dim
sr
As
New
StreamReader(fileName)
Do
Until
sr.Peek
=
-
1
Console.WriteLine(sr.ReadLine())
Loop
sr.Close()
End Sub
Sub
d()
Using
sr
As
New
StreamReader(fileName)
Do
Until
sr.EndOfStream
Console.WriteLine(sr.ReadLine())
Loop
End
Using
End Sub
Sub
e()
'
Read the entire contents of C:\test.doc in one shot.
Dim
sr
As
New
StreamReader(fileName)
Dim
fileContents
As
String
=
sr.ReadToEnd()
'
If the file is longer than 100 chars, process it again, one character at a
'
time (admittedly a silly thing to do, but it's just a demo).
If
fileContents.Length
>=
100
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.EndOfStream
'
Read method returns an integer, so convert it to Char.
Console.Write(sr.Read().ToString())
Loop
End
If
sr.Close()
End Sub
Sub
f()
'
By means of the CreateText static method of the File type
Dim
fileName
As
String
=
"
c:\text.dat
"
Dim
sw1
As
StreamWriter
=
File.CreateText(fileName)
'
By passing a FileStream from the Open method of the File class to
'
the StreamWriter's constructor method
Dim
st2
As
Stream
=
File.Open(fileName, 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
Dim
fs3
As
New
FileStream(fileName, FileMode.Open)
Dim
sw3
As
New
StreamWriter(fs3)
'
By getting a FileStream from the OpenWrite method of the File type
'
and passing it to the StreamWriter's constructor
Dim
sw4
As
New
StreamWriter(File.OpenWrite(fileName))
'
By passing the filename to the StreamWriter's constructor
Dim
sw5
As
New
StreamWriter(fileName)
'
Open the c:\test.dat file in append mode, be prepared to output
'
ASCII characters, and use a 2K buffer.
Dim
sw6
As
New
StreamWriter(
"
c:\test.new
"
,
True
, Encoding.ASCII,
2024
)
'
Terminate each line with a null character followed by a newline character.
sw6.NewLine
=
ControlChars.NullChar
&
ControlChars.NewLine
End Sub
'
This actually writes data to the file and closes it.
Sub
g()
Using
sr
As
New
StreamReader(
"
c:\test.txt
"
)
Using
sw
As
New
StreamWriter(
"
c:\test.new
"
)
Do
Until
sr.EndOfStream
sw.WriteLine(sr.ReadLine.ToUpper())
Loop
End
Using
End
Using
End Sub
'
使用内存获得更好的性能
Sub
h()
Using
sr
As
New
StreamReader(
"
c:\test.txt
"
), sw
As
New
StreamWriter(
"
c:\test.new
"
)
sw.WriteLine(sr.ReadToEnd().ToUpper())
End
Using
End Sub
End Module
15.7.4 读取和写入二进制文件
代码
Imports
System.IO
Module
Module6
Dim
fileName
As
String
=
"
c:\values.dat
"
Sub
a()
'
Associate a stream with a new file opened with write access.
Dim
st
As
Stream
=
File.Open(fileName, FileMode.Create, FileAccess.Write)
'
Create a BinaryWriter associated with the output stream.
Dim
bw
As
New
BinaryWriter(st)
'
Save 10 Double values to the file.
Dim
rand
As
New
Random()
For
i
As
Integer
=
1
To
10
bw.Write(rand.NextDouble())
Next
'
Flush the output data to the file.
bw.Close()
End Sub
'
Read back values written in previous code.
Sub
b()
'
Associate a stream with an existing file, opened with read access.
Dim
st2
As
Stream
=
File.Open(fileName, FileMode.Open, FileAccess.Read)
'
Create a BinaryReader associated with the input stream.
Using
br2
As
New
BinaryReader(st2)
'
Loop until data is available.
Do
Until
br2.PeekChar()
=
-
1
'
Read the next element. (We know it's a Double.)
Console.WriteLine(br2.ReadDouble())
Loop
'
Next statement closes both the BinaryReader and the underlying stream.
End
Using
End Sub
End Module
15.7.5 处理定长和分隔数据文件
代码
Imports
Microsoft.VisualBasic.FileIO
Imports
System.Text
Module
Module7
'
分界符文件
Sub
ReadDelimitedFiles()
Dim
fileName
As
String
=
"
data.txt
"
Dim
parser
As
New
TextFieldParser(fileName, Encoding.Default)
'
Field separator can be either a comma or a semicolon.
parser.Delimiters
=
New
String
() {
"
,
"
,
"
;
"
}
parser.TrimWhiteSpace
=
True
Do
Until
parser.EndOfData
Dim
fields()
As
String
=
parser.ReadFields()
'
Process each field in current record here.
Console.WriteLine(
"
First={0}, Last={1}, City={2}
"
, fields(
0
), fields(
1
), fields(
2
))
Loop
parser.Close()
End Sub
'
固定宽度文件
Sub
ReadFixedLengthFiles()
Using
parser
As
New
TextFieldParser(
"
data2.txt
"
, Encoding.Default)
parser.TextFieldType
=
FieldType.FixedWidth
parser.FieldWidths
=
New
Integer
() {
8
,
10
,
6
}
Do
Until
parser.EndOfData
Dim
fields()
As
String
=
parser.ReadFields()
Console.WriteLine(
"
First={0}, Last={1}, City={2}
"
, fields(
0
), fields(
1
), fields(
2
))
Loop
End
Using
End Sub
'
记录字段不一样
Sub
ReadTextFilesWithHeaders()
Using
parser
As
New
TextFieldParser(
"
data3.txt
"
, Encoding.Default)
parser.TextFieldType
=
FieldType.FixedWidth
Dim
headerWidths()
As
Integer
=
{
3
,
4
,
11
,
12
}
Dim
detailWidths()
As
Integer
=
{
3
,
6
,
18
,
6
}
parser.FieldWidths
=
headerWidths
Do
Until
parser.EndOfData
Dim
code
As
String
=
parser.PeekChars(
2
)
If
code
=
"
IH
"
Then
parser.FieldWidths
=
headerWidths
Dim
fields()
As
String
=
parser.ReadFields()
Console.WriteLine(
"
Invoice #{0}, Date={1}, Customer={2}
"
, fields(
1
), fields(
2
), fields(
3
))
ElseIf
code
=
"
ID
"
Then
parser.FieldWidths
=
detailWidths
Dim
fields()
As
String
=
parser.ReadFields()
Console.WriteLine(
"
#{0} {1} at ${2} each
"
, fields(
1
), fields(
2
), fields(
3
))
Else
Throw
New
MalformedLineException(
"
Invalid record code
"
)
End
If
Loop
End
Using
End Sub
End Module
15.8 其他Stream类型
15.8.1 内存流
代码
Imports
System.IO
Imports
System.Text
Imports
System.Globalization
Module
Module8
Sub
TestMemoryStream()
'
Create a memory stream with initial capacity of 1 KB.
Dim
st
As
New
MemoryStream(
1024
)
Dim
bw
As
New
BinaryWriter(st)
Dim
rand
As
New
Random()
'
Write 10 random Double values to the stream.
For
i
As
Integer
=
1
To
10
bw.Write(rand.NextDouble())
Next
'
Rewind the stream to the beginning and read back the data.
st.Seek(
0
, SeekOrigin.Begin)
Dim
br
As
New
BinaryReader(st)
Do
Until
br.PeekChar
=
-
1
Console.WriteLine(br.ReadDouble())
Loop
bw.Close()
br.Close()
st.Close()
End Sub
Sub
ReadWriteStrings()
Dim
st
As
New
MemoryStream(
1000
)
Dim
bw
As
New
BinaryWriter(st)
'
The BinaryWriter.Write method outputs a length-prefixed string.
bw.Write(
"
a length-prefixed string
"
)
'
We'll use this 1-KB buffer for both reading and writing.
Dim
buffer(
1023
)
As
Char
Dim
s
As
String
=
"
13 Characters
"
'
A fixed-length string
s.CopyTo(
0
, buffer,
0
, s.Length)
'
Copy into the buffer.
bw.Write(buffer,
0
, s.Length)
'
Output first 13 chars in buffer.
bw.Write(buffer,
0
, s.Length)
'
Do it a second time.
'
Rewind the stream, and prepare to read from it.
st.Seek(
0
, SeekOrigin.Begin)
Dim
br
As
New
BinaryReader(st)
'
Reading the length-prefixed string is simple.
Console.WriteLine(br.ReadString())
'
=> a length-prefixed string
'
Read the fixed-length string (13 characters) into the buffer.
br.Read(buffer,
0
,
13
)
s
=
New
String
(buffer,
0
,
13
)
'
Convert to a string.
Console.WriteLine(s)
'
=> 13 Characters
'
Another way to read a fixed-length string (13 characters)
'
(ReadChars returns a Char array that we can pass to the string constructor.)
s
=
New
String
(br.ReadChars(
13
))
Console.WriteLine(s)
'
=> 13 Characters
End Sub
End Module
15.8.2 基于字符串的流
代码
Imports
System.IO
Imports
System.Text
Imports
System.Globalization
Module
Module9
'
ReadLine
Sub
a()
Dim
veryLongString
As
String
=
""
Dim
strReader
As
New
StreamReader(veryLongString)
Do
Until
strReader.Peek
=
-
1
Console.WriteLine(strReader.ReadLine)
Loop
End Sub
Sub
StringWriterType()
'
Create a string with the space-separated abbreviated names of weekdays.
Dim
sb
As
New
StringBuilder()
'
The StringWriter associated with the StringBuilder
Dim
strWriter
As
New
StringWriter(sb)
'
Output day names to the string.
For
Each
d
As
String
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
End Module