C# 4 and .NET 4

eading and Writing to files ❘ 795
The simplest constructor takes just a filename. This StreamReader examines the byte order marks to
determine the encoding:
StreamReader sr = new StreamReader(@"C:\My Documents\ReadMe.txt");
Alternatively, you can specify that UTF8 encoding should be assumed:
StreamReader sr = new StreamReader(@"C:\My Documents\ReadMe.txt",
Encoding.UTF8);
You specify the encoding by using one of several properties on a class, System.Text.Encoding. This class
is an abstract base class, from which a number of classes are derived and which implements methods that
actually perform the text encoding. Each property returns an instance of the appropriate class, and the
possible properties you can use are here:
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ASCII
Unicode
UTF7
UTF8
UTF32
BigEndianUnicode
The following example demonstrates how to hook up a StreamReader to a FileStream. The advantage of
this is that you can specify whether to create the file and the share permissions, which you cannot do if you
directly attach a StreamReader to the file:
FileStream fs = new FileStream(@"C:\My Documents\ReadMe.txt",
FileMode.Open, FileAccess.Read, FileShare.None);
StreamReader sr = new StreamReader(fs);
For this example, you specify that the StreamReader will look for byte code markers to determine the
encoding method used, as it will do in the following examples, in which the StreamReader is obtained from
a FileInfo instance:
FileInfo myFile = new FileInfo(@"C:\My Documents\ReadMe.txt");
StreamReader sr = myFile.OpenText();
Just as with a FileStream, you should always close a StreamReader after use. Failure to do so will result in
the file remaining locked to other processes (unless you used a FileStream to construct the StreamReader
and specified FileShare.ShareReadWrite):
sr.Close();
Now that you have gone to the trouble of instantiating a StreamReader, you can do something with it. As
with the FileStream, you will simply see the various ways to read data, and the other, less commonly used
StreamReader methods are left to the SDK documentation.
Possibly the easiest method to use is ReadLine(), which keeps reading until it gets to the end of a line.
It does not include the carriage return–line feed combination that marks the end of the line in the
returned string:
string nextLine = sr.ReadLine();
Alternatively, you can grab the entire remainder of the file (or strictly, the remainder of the stream) in
one string:
string restOfStream = sr.ReadToEnd();
You can read a single character:
int nextChar = sr.Read();
This overload of Read() casts the returned character to an int. This is so that it has the option of returning
a value of -1 if the end of the stream has been reached.
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