C# 2008 Programmer's Reference

In addition to the File class, you have the FileInfo class that provides instance members for dealing with files. Once you have created an instance of the FileInfo class, you can use its members to obtain more information about a particular file. Figure 11-1 shows the different methods and properties exposed by an instance of the FileInfo class, such as the Attributes property, which retrieves the attributes of a file, the Delete() method that allows you to delete a file, and so on.

Figure 11-1

Reading and Writing to Files

The File class contains four methods to write content to a file:

□ WriteAllText() — Creates a file, writes a string to it, and closes the file

□ AppendAllText() — Appends a string to an existing file

□ WriteAllLines() — Creates a file, writes an array of string to it, and closes the file

□ WriteAllBytes() — Creates a file, writes an array of byte to it, and closes the file

The following statements show how to use the various methods to write some content to a file:

string filePath = @'C:	emp	extfile.txt';
string strTextToWrite = 'This is a string';
string[] strLinesToWrite = new string[] { 'Line1', 'Line2' };
byte[] bytesToWrite =
 ASCIIEncoding.ASCII.GetBytes('This is a string');
File.WriteAllText(filePath, strTextToWrite);
File.AppendAllText(filePath, strTextToWrite);
File.WriteAllLines(filePath, strLinesToWrite);
File.WriteAllBytes(filePath, bytesToWrite);

The File class also contains three methods to read contents from a file:

□ ReadAllText() — Opens a file, reads all text in it into a string, and closes the file

□ ReadAllLines() — Opens a file, reads all the text in it into a string array, and closes the file

□ ReadAllBytes() — Opens a file, reads all the content in it into a byte array, and closes the file

The following statements show how to use the various methods to read contents from a file:

string filePath = @'C:	emp	extfile.txt';
string strTextToRead = (File.ReadAllText(filePath));
string[] strLinestoRead = File.ReadAllLines(filePath);
byte[] bytesToRead = File.ReadAllBytes(filePath);

The beauty of these methods is that you need not worry about opening and closing the file after reading or writing to it; they close the file automatically after they are done.

StreamReader and StreamWriter Classes

When dealing with text files, you may also want to use the StreamReader and StreamWriter classes. StreamReader is derived from the TextReader class, an abstract class that represents a reader that can read a sequential series of characters.

You'll see more about streams in the 'The Stream Class' section later in this chapter.

The following code snippet uses the StreamReader class to read lines from a text file:

try {
 using (StreamReader sr = new StreamReader(filePath)) {
  string line;
  while ((line = sr.ReadLine()) != null) {
   Console.WriteLine(line);
  }
 }
} catch (Exception ex) {
 Console.WriteLine(ex.ToString());
}

In addition to the ReadLine() method, the StreamReader class supports the following methods:

□ Read() — Reads the next character from the input stream

□ ReadBlock() — Reads a maximum of specified characters

□ ReadToEnd() — Reads from the current position to the end of the stream

The StreamWriter class is derived from the abstract TextWriter class and is used for writing characters to a stream. The following code snippet uses the StreamWriter class to write lines to a text file:

try {
 using (StreamWriter sw = new StreamWriter(filePath)) {
  sw.Write('Hello, ');
  sw.WriteLine('World!');
 }
} catch (Exception ex) {
 Console.WriteLine(ex.ToString());
}

BinaryReader and BinaryWriter Classes

If you are dealing with binary files, you can use the BinaryReader and BinaryWriter classes. The following example reads binary data from one file and writes it into another, essentially making a copy of the file:

string filePath = @'C:	empVS2008Pro.png';
string filePathCopy = @'C:	empVS2008Pro_copy.png';
//---open files for reading and writing---
FileStream fs1 = File.OpenRead(filePath);
FileStream fs2 = File.OpenWrite(filePathCopy);
BinaryReader br = new BinaryReader(fs1);
BinaryWriter bw = new BinaryWriter(fs2);
//---read and write individual bytes---
for (int i = 0; i <= br.BaseStream.Length - 1; i++)
 bw.Write(br.ReadByte());
//---close the reader and writer---
br.Close();
bw.Close();

This program first uses the File class to open two files — one for reading and one for writing. The BinaryReader class is then used to read the binary data from the FileStream, and the BinaryWriter is used to write the binary data to the file.

The BinaryReader class contains many different read methods for reading different types of data — Read(), Read7BitEncodedInt(), ReadBoolean(), ReadByte(), ReadBytes(), ReadChar(), ReadChars()