C# 4 and .NET 4

796 ❘ ChaPTer 29 mAnipulAtinG files And the reGistry
Finally, you can read a given number of characters into an array, with an offset:
// to read 100 characters in.
int nChars = 100;
char [] charArray = new char[nChars];
int nCharsRead = sr.Read(charArray, 0, nChars);
nCharsRead will be less than nChars if you have requested to read more characters than are left in the file.
The streamWriter Class
This works in the same way as the StreamReader, except that you can use StreamWriter only to write to a
file (or to another stream). Possibilities for constructing a StreamWriter include this:
StreamWriter sw = new StreamWriter(@"C:\My Documents\ReadMe.txt");
This will use UTF8 encoding, which is regarded by .NET as the default encoding method. If you want, you
can specify alternative encoding:
StreamWriter sw = new StreamWriter(@"C:\My Documents\ReadMe.txt", true,
Encoding.ASCII);
In this constructor, the second parameter is a Boolean that indicates whether the file should be opened for
appending. There is, oddly, no constructor that takes only a filename and an encoding class.
Of course, you may want to hook up StreamWriter to a file stream to give you more control over the
options for opening the file:
FileStream fs = new FileStream(@"C:\My Documents\ReadMe.txt",
FileMode.CreateNew, FileAccess.Write, FileShare.Read);
StreamWriter sw = new StreamWriter(fs);
FileStream does not implement any methods that return a StreamWriter class.
Alternatively, if you want to create a new file and start writing data to it, you will find this sequence useful:
FileInfo myFile = new FileInfo(@"C:\My Documents\NewFile.txt");
StreamWriter sw = myFile.CreateText();
Just as with all other stream classes, it is important to close a StreamWriter class when you are finished
with it:
sw.Close();
Writing to the stream is done using any of 17 overloads of StreamWriter.Write(). The simplest writes out
a string:
string nextLine = "Groovy Line";
sw.Write(nextLine);
It is also possible to write out a single character:
char nextChar = 'a';
sw.Write(nextChar);
And an array of characters:
char [] charArray = new char[100];
// initialize these characters
sw.Write(charArray);
It is even possible to write out a portion of an array of characters:
int nCharsToWrite = 50;
int startAtLocation = 25;
char [] charArray = new char[100];
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