C using streams

Question

Streams are kind of mysterious to me  I don t know when to use which stream and how to use them  Can someone explain to me how streams are used   If I understand correctly  there are three stream types    stream read stream write stream   Is this correct  And  for example  what is the difference between a Memorystream and a FileStream

User · Answer

I would start by reading up on streams on MSDN: http://msdn.microsoft.com/en-us/library/system.io.stream.aspx

Memorystream and FileStream are streams used to work with raw memory and Files respectively...

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A stream is an object used to transfer data  There is a generic stream class System IO Stream  from which all other stream classes in  NET are derived  The Stream class deals with bytes   The concrete stream classes are used to deal with other types of data than bytes  For example    The FileStream class is used when the outside source is a file MemoryStream is used to store data in memory System Net Sockets NetworkStream handles network data   Reader writer streams such as StreamReader and StreamWriter are not streams - they are not derived from System IO Stream  they are designed to help to write and read data from and to stream

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Streams are good for dealing with large amounts of data  When it s impractical to load all the data into memory at the same time  you can open it as a stream and work with small chunks of it

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To expand a little on other answers here  and help explain a lot of the example code you ll see dotted about  most of the time you don t read and write to a stream directly  Streams are a low-level means to transfer data   You ll notice that the functions for reading and writing are all byte orientated  e g  WriteByte    There are no functions for dealing with integers  strings etc  This makes the stream very general-purpose  but less simple to work with if  say  you just want to transfer text   However   NET provides classes that convert between native types and the low-level stream interface  and transfers the data to or from the stream for you  Some notable such classes are   StreamWriter    Badly named  Should be TextWriter  StreamReader    Badly named  Should be TextReader  BinaryWriter BinaryReader   To use these  first you acquire your stream  then you create one of the above classes and associate it with the stream  E g   MemoryStream memoryStream   new MemoryStream    StreamWriter myStreamWriter   new StreamWriter memoryStream     StreamReader and StreamWriter convert between native types and their string representations then transfer the strings to and from the stream as bytes  So  myStreamWriter Write 123     will write  123   three characters  1    2  then  3   to the stream  If you re dealing with text files  e g  html   StreamReader and StreamWriter are the classes you would use   Whereas  myBinaryWriter Write 123     will write four bytes representing the 32-bit integer value 123  0x7B  0x00  0x00  0x00   If you re dealing with binary files or network protocols BinaryReader and BinaryWriter are what you might use   If you re exchanging data with networks or other systems  you need to be mindful of endianness  but that s another post

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Stream is just an abstraction  or a wrapper  over a physical stream of bytes  This physical stream is called the base stream  So there is always a base stream over which a stream wrapper is created and thus the wrapper is named after the base stream type ie FileStream  MemoryStream etc   The advantage of the stream wrapper is that you get a unified api to interact with streams of any underlying type usb  file etc   Why would you treat data as stream - because data chunks are loaded on-demand  we can inspect process the data as chunks rather than loading the entire data into memory  This is how most of the programs deal with big files  for eg encrypting an OS image file

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I wouldn t call those different kind of streams  The Stream class have CanRead and CanWrite properties that tell you if the particular stream can be read from and written to   The major difference between different stream classes  such as MemoryStream vs FileStream  is the backing store - where the data is read from or where it s written to  It s kind of obvious from the name  A MemoryStream stores the data in memory only  a FileStream is backed by a file on disk  a NetworkStream reads data from the network and so on

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There is only one basic type of Stream   However in various circumstances some members will throw an exception when called because in that context the operation was not available   For example a MemoryStream is simply a way to moves bytes into and out of a chunk of memory   Hence you can call Read and Write on it   On the other hand a FileStream allows you to read or write  or both  from to a file   Whether you can actually Read or Write depends on how the file was opened   You can t Write to a file if you only opened it for Read access

[c#] C# using streams

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