First contact with C # asynchronous programming

C # There are four asynchronous programming methods. refer to the following Article
Msdn-asynchronous programming Overview [C #]
In addition, the msdn help documentation also provides relevant introductions.
Msdn: MS-help: // Ms. vscc.2003/ms. msdnqtr.2003feb. 2052/cpgenref/html/cpconasynchronousexecution.htm
In addition, you can achieve the same effect (I have not used it ):
// System. Threading. threadpool. queueuserworkitem (new system. Threading. waitcallback (dodownloadwork), null );

Below is a piece of practiceProgram(Many attribute fields are saved ):

Namespace Hooyee. FTP {
Public   Class Filedownloader {
Public Filedownloader () {
}

Iftpdownloader members # Region Iftpdownloader members

Private   Delegate   Void Asyncdownloaddelegate (filestream );

Public   Void Start () {
Iresult < Filestream > Resultstream;
Resultstream = ( New Localfileaccess (). appendfile (_ saveas ); // _ Saveas is a field of the class and its definition is omitted.

Asyncdownloaddelegate asyncdownloaddlg =   New Asyncdownloaddelegate (dodownloadwork );
Iasyncresult ar = Asyncdownloaddlg. begininvoke (resultstream. object, New Asynccallback (downloadfinished), asyncdownloaddlg );

// System. Threading. threadpool. queueuserworkitem (new system. Threading. waitcallback (dodownloadwork), null );
}


Private   Void Dodownloadwork (filestream) {
Ftpwebresponse response =   Null ;
Stream stream =   Null ;
Try   {
Response = (Ftpwebresponse) _ request. getresponse ();
Stream = Response. getresponsestream ();
Int Reads =   0 ;
Byte [] Buffer =   New Byte [buffer_size];
Binarywriter writer =   New Binarywriter (filestream );
While (Reads = Stream. Read (buffer, 0 , Buffer_size )) >   0 ) {
Writer. Write (buffer,0, Reads );
}
}   Catch (Ioexception ex) {
//Ftplog log = new ftplog ();
//Log. Write
}   Catch (Exception ex) {
}   Finally   {
If (Stream ! =   Null ) Stream. Close ();
If (Filestream ! =   Null ) Filestream. Close ();
If (Response ! =   Null ) Response. Close ();
}
}

Private   Void Downloadfinished (iasyncresult AR) {
Asyncdownloaddelegate dlgt = (Asyncdownloaddelegate) Ar. asyncstate;
Dlgt. endinvoke (AR );
Try   {
//Modify the file name after the download is complete.
Localfileaccess. Rename (_ saveas );
}   Catch   {
}
If (Onfinished ! =   Null ) {
Ftpnoticeeventargs E= NewFtpnoticeeventargs (_ remotefile,0, Ftpdownloadactions. Finish );
Onfinished (This, E );
}
}
# Endregion
}
}