Chapter109:Stream

Section109.1:UsingStreams

Astreamisanobjectthatprovidesalow-levelmeanstotransferdata.Theythemselvesdonotactasdata containers.

Thedatathatwedealwithisinformofbytearray(byte[]).Thefunctionsforreadingandwritingareallbyte orientated, e.g. WriteByte().

Therearenofunctionsfordealingwithintegers,stringsetc.Thismakesthestreamverygeneral-purpose,butless simpletoworkwithif,say,youjustwanttotransfertext.Streamscanbeparticularlyveryhelpfulwhenyouare dealing with large amount of data.

WewillneedtousedifferenttypeofStreambasedwhereitneedstobewritten/readfrom(i.e.thebackingstore). Forexample,ifthesourceisafile,weneedtouseFileStream:

stringfilePath=@”c:\Users\exampleuser\Documents\userinputlog.txt”;

using(FileStreamfs=newFileStream(filePath,FileMode.Open,FileAccess.Read, FileShare.ReadWrite))

{

//dostuffhere…

fs.Close();

}

Similarly,MemoryStreamisusedifthebackingstoreismemory:

//Readallbytesinfromafileonthedisk.

byte[]file=File.ReadAllBytes(“C:\\file.txt”);

//Createamemorystreamfromthosebytes.

using(MemoryStreammemory=newMemoryStream(file))

{

//dostuffhere…

}

Similarly,System.Net.Sockets.NetworkStreamisusedfornetworkaccess.

AllStreamsarederivedfromthegenericclassSystem.IO.Stream.Datacannotbedirectlyreadorwrittenfrom streams.The.NETFrameworkprovideshelperclassessuchasStreamReader,StreamWriter,BinaryReaderand BinaryWriterthatconvertbetweennativetypesandthelow-levelstreaminterface,andtransferthedatatoor from the stream for you.

ReadingandwritingtostreamscanbedoneviaStreamReaderandStreamWriter.Oneshouldbecarefulwhen closingthese.Bydefault,closingwillalsoclosecontainedstreamaswellandmakeitunusableforfurtheruses.This defaultbehaviourcanbechangebyusingaconstructorwhichhasboolleaveOpenparameterandsettingitsvalue as true.

StreamWriter:

FileStreamfs=newFileStream(“sample.txt”,FileMode.Create);

StreamWritersw=newStreamWriter(fs);

stringNextLine=”Thisistheappendedline.”; sw.Write(NextLine);

sw.Close();

//fs.Close();Thereisnoneedtoclosefs.Closingswwillalsoclosethestreamitcontains.

StreamReader:

using(varms=newMemoryStream())

{

StreamWritersw=newStreamWriter(ms); sw.Write(123);

//sw.Close();                Thiswillclosemsandwhenwetrytousemslateritwillcauseanexception

sw.Flush();               //Youcansendtheremainingdatatostream.Closingwilldothisautomatically

//Weneedtosetthepositionto0inordertoread

//fromthebeginning.

ms.Position=0;

StreamReadersr=newStreamReader(ms);

varmyStr=sr.ReadToEnd();sr.Close();

ms.Close();

}

SinceClassesStream,StreamReader,StreamWriter,etc.implementtheIDisposableinterface,wecancallthe

Dispose()methodon objectsof theseclasses.