в 15:31, 26 мая 2010

2010-05-26T15:31:19Z

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2010-05-26T11:45:40Z

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==A help program that uses a disk file to store help information==

<source lang="csharp">
/*
C# A Beginner"s Guide
By Schildt
Publisher: Osborne McGraw-Hill
ISBN: 0072133295
*/
/*
Project 11-2

A help program that uses a disk file
to store help information.
*/

using System;
using System.IO;

/* The Help class opens a help file,
searches for a topic, and then displays
the information associated with that topic. */
class Help {
string helpfile; // name of help file

public Help(string fname) {
helpfile = fname;
}

// Display help on a topic.
public bool helpon(string what) {
StreamReader helpRdr;
int ch;
string topic, info;

try {
helpRdr = new StreamReader(helpfile);
}
catch(FileNotFoundException exc) {
Console.WriteLine(exc.Message);
return false;
}

try {
do {
// read characters until a # is found
ch = helpRdr.Read();

// now, see if topics match
if(ch == "#") {
topic = helpRdr.ReadLine();
if(what == topic) { // found topic
do {
info = helpRdr.ReadLine();
if(info != null) Console.WriteLine(info);
} while((info != null) && (info != ""));
helpRdr.Close();
return true;
}
}
} while(ch != -1);
}
catch(IOException exc) {
Console.WriteLine(exc.Message);
}
helpRdr.Close();
return false; // topic not found
}

// Get a Help topic.
public string getSelection() {
string topic = "";

Console.Write("Enter topic: ");
try {
topic = Console.ReadLine();
}
catch(IOException exc) {
Console.WriteLine(exc.Message);
return "";
}
return topic;
}
}

// Demonstrate the file-based Help system.
public class FileHelp {
public static void Main() {
Help hlpobj = new Help("helpfile.txt");
string topic;

Console.WriteLine("Try the help system. " +
"Enter "stop" to end.");
do {
topic = hlpobj.getSelection();

if(!hlpobj.helpon(topic))
Console.WriteLine("Topic not found.\n");

} while(topic != "stop");
}
}
/*
#if
if(condition) statement;
else statement;
#switch
switch(expression) {
case constant:
statement sequence
break;
// ...
}
#for
for(init; condition; iteration) statement;
#while
while(condition) statement;
#do
do {
statement;
} while (condition);
#break
break; or break label;
#continue
continue; or continue label;
#goto
goto label;

*/

</source>

==A simple key-to-disk utility that demonstrates a StreamWriter==

<source lang="csharp">
/*
C#: The Complete Reference
by Herbert Schildt
Publisher: Osborne/McGraw-Hill (March 8, 2002)
ISBN: 0072134852
*/
/* A simple key-to-disk utility that
demonstrates a StreamWriter. */

using System;
using System.IO;

public class KtoD {
public static void Main() {
string str;
FileStream fout;

try {
fout = new FileStream("test.txt", FileMode.Create);
}
catch(IOException exc) {
Console.WriteLine(exc.Message + "Cannot open file.");
return ;
}
StreamWriter fstr_out = new StreamWriter(fout);

Console.WriteLine("Enter text ("stop" to quit).");
do {
Console.Write(": ");
str = Console.ReadLine();

if(str != "stop") {
str = str + "\r\n"; // add newline
try {
fstr_out.Write(str);
} catch(IOException exc) {
Console.WriteLine(exc.Message + "File Error");
return ;
}
}
} while(str != "stop");

fstr_out.Close();
}
}

</source>

==Asynchronously reads a stream==

<source lang="csharp">
/*
C# Programming Tips & Techniques
by Charles Wright, Kris Jamsa
Publisher: Osborne/McGraw-Hill (December 28, 2001)
ISBN: 0072193794
*/
// Async.cs -- Asynchronously reads a stream
//
// Compile this program with the following command line;
// C:>csc Async.cs
//
using System;
using System.IO;
using System.Threading;
namespace nsStreams
{
public class Async
{
static Byte [] data = new Byte[64];
static bool bDone = true;
static public void Main (string [] args)
{
if (args.Length == 0)
{
Console.WriteLine ("Please enter a file name");
return;
}
FileStream istrm;
try
{
istrm = new FileStream (args[0], FileMode.Open,
FileAccess.Read, FileShare.Read,
data.Length, true);
}
catch (FileNotFoundException)
{
Console.WriteLine (args[0] + " was not found");
return;
}
catch (Exception)
{
Console.WriteLine ("Cannot open " + args[0] +
" for reading");
return;
}
AsyncCallback cb = new AsyncCallback (ShowText);
long Length = istrm.Length;
int count = 0;
while (true)
{
if (Length == istrm.Position)
break;
if (bDone)
{
bDone = false;
istrm.BeginRead (data, 0, data.Length, cb, count);
++count;
}
Thread.Sleep (250);
}
istrm.Close ();
}
static public void ShowText (IAsyncResult result)
{
for (int x = 0; x < data.Length; ++x)
{
if (data[x] == 0)
break;
Console.Write ((char) data[x]);
data[x] = 0;
}
bDone = true;
}
}
}

</source>

==Catch file read exception and retry==

<source lang="csharp">
using System;
using System.IO;
class Retry {
static void Main() {
StreamReader sr;
int attempts = 0;
int maxAttempts = 3;
GetFile:
Console.Write("\n[Attempt #{0}] Specify file " + "to open/read: ", attempts + 1);
string fileName = Console.ReadLine();
try {
sr = new StreamReader(fileName);
string s;
while (null != (s = sr.ReadLine())) {
Console.WriteLine(s);
}
sr.Close();
} catch (FileNotFoundException e) {
Console.WriteLine(e.Message);
if (++attempts < maxAttempts) {
Console.Write("Do you want to select another file: ");
string response = Console.ReadLine();
response = response.ToUpper();
if (response == "Y") goto GetFile;
} else {
Console.Write("You have exceeded the maximum retry limit ({0})", maxAttempts);
}
} catch (Exception e) {
Console.WriteLine(e.Message);
}
}
}
</source>

==Construct StreamWriter from FileSream==

<source lang="csharp">
using System;
using System.IO;
public class IOExample
{
static void Main() {
FileStream fs;
StreamWriter sw;

try {
fs = new FileStream("practice.txt", FileMode.Open );
sw = new StreamWriter(fs);
// write a line to the file
string newLine = "Not so different from you and me";
sw.WriteLine(newLine);
// close the streams
sw.Close();
fs.Close();
} catch (IOException ioe) {
Console.WriteLine("IOException occurred: "+ioe.Message);
}
}
}

</source>

==Create a StreamWriter in UTF8 mode==

<source lang="csharp">
using System;
using System.IO;
using System.Text;
class MainClass {
static void Main() {
using (FileStream fs = new FileStream("test.txt", FileMode.Create)) {
using (StreamWriter w = new StreamWriter(fs, Encoding.UTF8)) {
w.WriteLine(124.23M);
w.WriteLine("Test string");
w.WriteLine("!");
}
}
using (FileStream fs = new FileStream("test.txt", FileMode.Open)) {
using (StreamReader r = new StreamReader(fs, Encoding.UTF8)) {
Console.WriteLine(Decimal.Parse(r.ReadLine()));
Console.WriteLine(r.ReadLine());
Console.WriteLine(Char.Parse(r.ReadLine()));
}
}
}
}
</source>

==Demonstrates attaching a StreamReader object to a stream==

<source lang="csharp">
/*
C# Programming Tips & Techniques
by Charles Wright, Kris Jamsa
Publisher: Osborne/McGraw-Hill (December 28, 2001)
ISBN: 0072193794
*/
// StrmRdr.cs -- Demonstrates attaching a StreamReader object to a stream
//
// Compile this program with the following command line:
// C:>csc StrmRdr.cs
using System;
using System.IO;
namespace nsStreams
{
public class StrmRdr
{
static public void Main (string [] args)
{
if (args.Length == 0)
{
Console.WriteLine ("Please enter a file name");
return;
}
FileStream strm;
StreamReader reader;
try
{
// Create the stream
strm = new FileStream (args[0], FileMode.Open, FileAccess.Read);
// Link a stream reader to the stream
reader = new StreamReader (strm);
}
catch (Exception e)
{
Console.WriteLine (e.Message);
Console.WriteLine ("Cannot open " + args[0]);
return;
}
while (reader.Peek() >= 0)
{
string text = reader.ReadLine ();
Console.WriteLine (text);
}
reader.Close ();
strm.Close ();
}
}
}

</source>

==Demonstrates attaching a StreamWriter object to a stream==

<source lang="csharp">
/*
C# Programming Tips & Techniques
by Charles Wright, Kris Jamsa
Publisher: Osborne/McGraw-Hill (December 28, 2001)
ISBN: 0072193794
*/
// StrmWrtr.cs -- Demonstrates attaching a StreamWriter object to a stream
//
// Compile this program with the following command line:
// C:>csc StrmWrtr.cs
using System;
using System.IO;
namespace nsStreams
{
public class StrmWrtr
{
static public void Main (string [] args)
{
if (args.Length == 0)
{
Console.WriteLine ("Please enter a file name");
return;
}
FileStream strm;
StreamWriter writer;
try
{
// Create the stream
strm = new FileStream (args[0], FileMode.OpenOrCreate, FileAccess.Write);
// Link a stream reader to the stream
writer = new StreamWriter (strm);
}
catch (Exception e)
{
Console.WriteLine (e.Message);
Console.WriteLine ("Cannot open " + args[0]);
return;
}
strm.SetLength (0);
while (true)
{
string str = Console.ReadLine ();
if (str.Length == 0)
break;
writer.WriteLine (str);
}
writer.Close ();
strm.Close ();
}
}
}

</source>

==illustrates reading and writing text data==

<source lang="csharp">
/*
Mastering Visual C# .NET
by Jason Price, Mike Gunderloy
Publisher: Sybex;
ISBN: 0782129110
*/
/*
Example15_16.cs illustrates reading and writing text data
*/
using System;
using System.IO;
public class Example15_16
{
public static void Main()
{
// create a new file to work with
FileStream outStream = File.Create("c:\\TextTest.txt");
// use a StreamWriter to write data to the file
StreamWriter sw = new StreamWriter(outStream);
// write some text to the file
sw.WriteLine("This is a test of the StreamWriter class");
// flush and close
sw.Flush();
sw.Close();
// now open the file for reading
StreamReader sr = new StreamReader("c:\\TextTest.txt");
// read the first line of the file into a buffer and display it
string FirstLine;

FirstLine = sr.ReadLine();
Console.WriteLine(FirstLine);
// clean up
sr.Close();
}
}

</source>

==Open a file using StreamWriter==

<source lang="csharp">
/*
C#: The Complete Reference
by Herbert Schildt
Publisher: Osborne/McGraw-Hill (March 8, 2002)
ISBN: 0072134852
*/
// Open a file using StreamWriter.

using System;
using System.IO;

public class KtoD1 {
public static void Main() {
string str;
StreamWriter fstr_out;

// Open the file directly using StreamWriter.
try {
fstr_out = new StreamWriter("test.txt");
}
catch(IOException exc) {
Console.WriteLine(exc.Message + "Cannot open file.");
return ;
}

Console.WriteLine("Enter text ("stop" to quit).");
do {
Console.Write(": ");
str = Console.ReadLine();

if(str != "stop") {
str = str + "\r\n"; // add newline
try {
fstr_out.Write(str);
} catch(IOException exc) {
Console.WriteLine(exc.Message + "File Error");
return ;
}
}
} while(str != "stop");

fstr_out.Close();
}
}

</source>

==Read data in line by line==

<source lang="csharp">
using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
class Program {
static void Main(string[] args) {
string strLine;
try {
FileStream aFile = new FileStream("Log.txt", FileMode.Open);
StreamReader sr = new StreamReader(aFile);
strLine = sr.ReadLine();
while (strLine != null) {
Console.WriteLine(strLine);
strLine = sr.ReadLine();
}
sr.Close();
} catch (IOException e) {
Console.WriteLine("An IO exception has been thrown!");
Console.WriteLine(e.ToString());
return;
}
}
}
</source>

==Reading from a text file line by line==

<source lang="csharp">

using System;
using System.IO;
class MainClass {
public static void Main(string[] args) {
try {
FileStream fs = new FileStream("c:\\a.txt", FileMode.Open);
StreamReader sr = new StreamReader(fs);
string line = "";
int lineNo = 0;
do {
line = sr.ReadLine();
if (line != null) {
Console.WriteLine("{0}: {1}", lineNo, line);
lineNo++;
}
} while (line != null);
} catch (Exception e) {
Console.WriteLine("Exception in ShowFile: {0}", e);
}
}
}
</source>

==StreamReader And Writer==

<source lang="csharp">
/*
* C# Programmers Pocket Consultant
* Author: Gregory S. MacBeth
* Email: gmacbeth@comporium.net
* Create Date: June 27, 2003
* Last Modified Date:
* Version: 1
*/
using System;
using System.IO;
namespace Client.Chapter_11___File_and_Streams
{
public class StreamReaderAndWriter {
static void Main(string[] args)
{
StreamReader MyStreamReader = new StreamReader(@"c:\Projects\Testing.txt");
//If you need to control share permissions when creating a file you
//use FileStream with StreamReader
FileStream MyFileStream = new FileStream(@"c:\Projects\Testing.txt", FileMode.Open, FileAccess.Read, FileShare.None);
StreamReader MyStreamReader2 = new StreamReader(MyFileStream);
MyFileStream.Close();
MyStreamReader2.Close();
//The easiest way to Read a stream is to use the ReadLine method.
//This method reads until it gets to the end of a line, but ...
//it does not copy the carriage return line feed /n/r.
string MyStringReader = MyStreamReader.ReadLine();
//You can also read the whole file by using the following
string MyStringReadToEOF = MyStreamReader.ReadToEnd();
//The other route is to read one character at a time
int[] MyArrayOfCharacters = new int[100];
for (int i = 0; i < 99; i++)
{
MyArrayOfCharacters[i] = MyStreamReader.Read();
}
MyStreamReader.Close();
}
}
}

</source>

==StreamReader.ReadLine==

<source lang="csharp">
using System;
using System.IO;
public class MainClass {
public static void Main() {
FileStream fs2 = File.Create("Bar.txt");
StreamWriter w2 = new StreamWriter(fs2);
w2.Write("Goodbye Mars");
w2.Close();
fs2 = File.Open("Bar.txt", FileMode.Open, FileAccess.Read, FileShare.None);
StreamReader r2 = new StreamReader(fs2);
String t;
while ((t = r2.ReadLine()) != null) {
Console.WriteLine(t);
}
w2.Close();
fs2.Close();
}
}
</source>

==The use of a buffered stream to serve as intermediate data holder for another stream==

<source lang="csharp">
/*
C# Programming Tips & Techniques
by Charles Wright, Kris Jamsa
Publisher: Osborne/McGraw-Hill (December 28, 2001)
ISBN: 0072193794
*/
// BufStrm.cs -- demonstates the use of a buffered stream to serve
// as intermediate data holder for another stream.
//
// Compile this program with the following command line:
// C:>csc BufStrm.cs
using System;
using System.IO;
namespace nsStreams
{
public class BufStrm
{
static public void Main ()
{
FileStream strm;
try
{
strm = new FileStream ("./BufStrm.txt",
FileMode.OpenOrCreate,
FileAccess.Write);
}
catch (Exception e)
{
Console.WriteLine (e.Message);
Console.WriteLine ("Cannot open ./BufStrm.txt");
return;
}
strm.SetLength (0);
BufferedStream bstrm = new BufferedStream (strm);
string str = "Now is the time for all good men to " +
"come to the aid of their Teletype.\r\n";
byte [] b;
StringToByte (out b, str);
bstrm.Write (b, 0, b.Length);
// Save the current position to fix an error.
long Pos = bstrm.Position;
Console.WriteLine ("The buffered stream position is "
+ bstrm.Position);
Console.WriteLine ("The underlying stream position is "
+ strm.Position);
str = "the quick red fox jumps over the lazy brown dog.\r\n";
StringToByte (out b, str);
bstrm.Write (b, 0, b.Length);
Console.WriteLine ("\r\nThe buffered stream position is " +
bstrm.Position);
Console.WriteLine ("The underlying stream position is still "
+ strm.Position);
// Fix the lower case letter at the beginning of the second string
bstrm.Seek (Pos, SeekOrigin.Begin);
b[0] = (byte) "T";
bstrm.Write (b, 0, 1);
// Flush the buffered stream. This will force the data into the
// underlying stream.
bstrm.Flush ();
bstrm.Close ();
strm.Close ();
}
//
// Convert a buffer of type string to byte
static void StringToByte (out byte [] b, string str)
{
b = new byte [str.Length];
for (int x = 0; x < str.Length; ++x)
{
b[x] = (byte) str [x];
}
}
}
}

//File: BufStrm.txt
/*
Now is the time for all good men to come to the aid of their Teletype.
The quick red fox jumps over the lazy brown dog.
*/

</source>

==Try and catch exceptions for StreamWriter==

<source lang="csharp">
/*
* C# Programmers Pocket Consultant
* Author: Gregory S. MacBeth
* Email: gmacbeth@comporium.net
* Create Date: June 27, 2003
* Last Modified Date:
*/
using System;
using System.IO;
namespace Client.Chapter_9___Exceptions_and_AppDomains
{
public class MyMainClassChapter_9___Exceptions_and_AppDomains
{
delegate int MyDelegate(string s);
static void Main(string[] args)
{
StreamWriter MyStream = null;
string MyString = "Hello World";
try
{
MyStream = File.CreateText("MyFile.txt");
MyStream.Write(MyString);
}
catch (IOException e)
{
Console.WriteLine(e);
}
catch (Exception e)
{
Console.WriteLine(e);
}
finally
{
if (MyStream != null)
MyStream.Close();
}
}
}
public class MyFile
{
public StreamWriter WriteText(string s)
{
if (!Valid(s))
throw new IOException("Can"t Write String");
else
return new StreamWriter("c:\\test.txt");
}
public bool Valid(string s)
{
return false;
}
}
}

</source>

==Use StreamWriter to create a text file==

<source lang="csharp">
using System;
using System.IO;

public class MyStreamWriterReader {
static void Main(string[] args) {
StreamWriter writer = new StreamWriter("reminders.txt");
writer.WriteLine("...");
writer.WriteLine("Don"t forget these numbers:");
for (int i = 0; i < 10; i++)
writer.Write(i + " ");
writer.Write(writer.NewLine);
writer.Close();
StreamReader sr = new StreamReader("reminders.txt");
string input = null;
while ((input = sr.ReadLine()) != null) {
Console.WriteLine(input);
}
}
}
</source>

==Using StreamWriter 3==

<source lang="csharp">
/*
* C# Programmers Pocket Consultant
* Author: Gregory S. MacBeth
* Email: gmacbeth@comporium.net
* Create Date: June 27, 2003
* Last Modified Date:
* Version: 1
*/
using System;
using System.IO;
namespace Client.Chapter_11___File_and_Streams
{
public class UsingStreamWriter {
static void Main(string[] args)
{
//StreamWriter can only be use to write to files or other streams
StreamWriter MyStreamWriter = new StreamWriter(@"c:\Projects\Testing.txt");
//You can also use FileStream with StreamWriter to provide a greater degree of control
//in how you open the file
FileStream MyFileStream = new FileStream(@"c:\Projects\Testing.txt", FileMode.CreateNew, FileAccess.Write, FileShare.None);
StreamWriter MyStreamWriter2 = new StreamWriter(MyFileStream);
MyFileStream.Close();
MyStreamWriter2.Close();
//You can write sequentially to a file using this technique
FileInfo MyFile = new FileInfo(@"c:\Projects\Testing.txt");
StreamWriter MyStreamWriter3 = MyFile.CreateText();
MyStreamWriter3.Close();
//There are four overloaded ways to use StreamWriter.Write()
//Writes a stream to a file
string MyString = "Hello World";
MyStreamWriter.Write(MyString);
//Writes single characters to a stream
char MyChar = "A";
MyStreamWriter.Write(MyChar);
//Writes an Array of characters
char[] MyCharArray = new char[100];
for (int i = 0; i < 99; i++)
{
MyCharArray[i] = (char)i;
}
MyStreamWriter.Write(MyCharArray);
//or you can write a portion of an array
MyStreamWriter.Write(MyCharArray, 25, 30);
MyStreamWriter.Close();
}
}
}

</source>

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