Reading Data
Before you learn about reading XML, you must learn how to read a file. In this section, I’ll cover basic filesystem and network input in .NET. If you’re already familiar with basic I/O types and methods in .NET, feel free to skip to the next section.
I/O
classes in .NET are located in the System.IO
namespace. The basic object used for reading and writing data,
regardless of the source, is the Stream
object.
Stream
is an abstract base class, which represents
a sequence of bytes; the Stream
has a
Read( )
method to read the bytes from the
Stream
, a Write( )
method to
write bytes to the Stream
, and a Seek(
)
method to set the current location within the
Stream
. Not all instances or subclasses of
Stream
support all these operations; for example,
you cannot write to a FileStream
representing a
read-only file, and you cannot Seek( )
to a
position in a NetworkStream
. The properties
CanRead
, CanWrite
, and
CanSeek
can be interrogated to determine whether
the respective operations are supported by the instance of
Stream
you’re dealing with.
Table 2-1 shows the Stream
type’s subclasses and the methods each type
supports.
Type |
Length |
Position |
Flush( ) |
Read( ) |
Seek( ) |
Write( ) |
|
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
|
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
|
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
|
Yes ... |
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