Loading Levels from Files - Learning C# by Programming Games - page 291

• an XMLReader reads XML things from an underlying stream

• a TextReader reads text things from an underlying something

• a StreamReader reads text things from an underlying stream

• a StringReader reads text things from an underlying string

The confusing thing is that the name of the reader sometimes indicates what is being
read, and sometimes from where it is reading data.

22.5.5 Stream Reader

The most common way to read a file is by using a StreamReader object. This is a
TextReader using an underlying stream, meaning that if you want to use this kind of
reader, you first need to have a Stream . There are many different kinds of streams, but
again the most common one is the FileStream .Usingthe FileStream in combination
with a StreamReader is illustrated by the following lines of code:

FileStream s = new FileStream("test.txt", FileMode.Open);
StreamReader r = new StreamReader(s);
string t = r.ReadToEnd();

Because of the highly common combination of the StreamReader with the FileStream ,
the StreamReader class has a constructor that takes a file name as parameter and that
creates the FileStream object itself. A FileMode parameter is no longer necessary in
this case, because we always want to open an existing file when reading. So, what
remains is the following code:

StreamReader r = new StreamReader("test.txt");
string t = r.ReadToEnd();

By the way, there is an even shorter way to read all the text from a file, because
the File class has a static method ReadAllText that creates the StreamReader and calls
ReadToEnd . This results in the following (single line of) code:

string t = File.ReadAllText("test.txt");

The libraries available in C# have many of these shortcuts, but sometimes you may
want to do something slightly different from what the shortcut dictates. In that case,
you need to take the long approach and you need to know how everything works
behind the scenes.

22.5.6 Abstract Classes

We mentioned earlier on that TextReader is an abstract class. The Stream , Tex t W r i t e r ,
XmlReader and XmlWriter classes are also abstract. This means that it is not allowed to