Binary | data | database | Asynchronous mode one: Fetch at a time, write asynchronously
<summary>
Buffer size
</summary>
public const INT NUMPIXELS = 512 * 512;
<summary>
Writing data files to disk
</summary>
<param name= "strSQL" ></param>
<returns></returns>
public static bool Makefilewithwritelistbyadapter (string Strsql,out string strerr)
{
if (File.exists (Configproxy.getvaluebykey ("ListFile"))) File.delete (Configproxy.getvaluebykey ("ListFile"));
DataTable objtable;
if (! Oledatabaseproxy.executesql (strsql,out objtable,out strerr)) return false;
String OutputPath = Configproxy.getvaluebykey ("OutputPath");
if (ObjTable.Rows.Count < 1) return false;
String strdirectory = OutputPath + "\";
if (! Directory.Exists (strdirectory)) directory.createdirectory (strdirectory);
for (int i = 0;i< ObjTable.Rows.Count; i + +)
{
String fileName = objtable.rows[i]["attachment name"]. ToString ();
Record Output list
Logproxy.writelist (strdirectory + fileName);
Get File Data
byte [] imagecontent = (byte[]) objtable.rows[i]["attachment content"];
AutoResetEvent manualevent = new AutoResetEvent (false);
FileStream FStream =
New FileStream (Strdirectory + filename,filemode.create,
FileAccess.ReadWrite, Fileshare.none, 4096, true);
IAsyncResult asyncresult = Fstream.beginwrite (
Imagecontent, 0, Imagecontent.length,
New AsyncCallback (Endwritecallback),
New State (FStream, manualevent));
Manualevent.waitone (5000, false);
Fstream.close ();
}
Strerr = "";
return true;
}
Class State
{
Public FileStream FStream;
public AutoResetEvent autoevent;
Public State (FileStream FStream, AutoResetEvent autoevent)
{
This.fstream = FStream;
This.autoevent = autoevent;
}
}
static void Endwritecallback (IAsyncResult asyncresult)
{
state Stateinfo = (state) asyncresult.asyncstate;
int workerthreads;
int portthreads;
Try
{
Threadpool.getavailablethreads (out WorkerThreads,
Out portthreads);
StateInfo.fStream.EndWrite (asyncresult);
Thread.Sleep (1500);
}
Finally
{
StateInfo.autoEvent.Set ();
}
}
Mode two: Read online, asynchronous write
<summary>
Buffer size
</summary>
public const INT NUMPIXELS = 512 * 512;
<summary>
Writing data files to disk
</summary>
<param name= "strSQL" ></param>
<returns></returns>
public static bool Makefilewithwritelistbyreader (string Strsql,out string strerr)
{
if (File.exists (Configproxy.getvaluebykey ("ListFile"))) File.delete (Configproxy.getvaluebykey ("ListFile"));
String OutputPath = Configproxy.getvaluebykey ("OutputPath");
String strdirectory = OutputPath + "\";
if (! Directory.Exists (strdirectory)) directory.createdirectory (strdirectory);
System.Data.OleDb.OleDbCommand cmd = new OleDbCommand ();
OleDbConnection Cnn = new OleDbConnection (Configproxy.getvaluebykey ("oleconnectionstring"));
Cmd. Connection = Cnn;
Cmd.commandtext = strSQL;
Open connection
Try
{
Cnn.open ();
}
catch (Exception ERR)
{
Strerr = Err.message;
return false;
}
byte[] pixels = new Byte[numpixels];
OleDbDataReader reader = cmd. ExecuteReader ();
Byte[]imagecontent;
Process-by-article
while (reader. Read ())
{
String fileName = reader. GetString (1);
Record Output list
Logproxy.writelist (strdirectory + fileName);
Get File Data
Imagecontent = new Byte[convert.toint64 (reader. GetString (7))];
Reader. GetBytes (6,0,imagecontent,0,convert.toint32 Reader. GetString (7)));
AutoResetEvent manualevent = new AutoResetEvent (false);
FileStream FStream =
New FileStream (Strdirectory + filename,filemode.create,
FileAccess.ReadWrite, Fileshare.none, 4096, true);
IAsyncResult asyncresult = Fstream.beginwrite (
Imagecontent, 0, Imagecontent.length,
New AsyncCallback (Endwritecallback),
New State (FStream, manualevent));
Manualevent.waitone (5000, false);
Fstream.close ();
}
Reader. Close ();
Close connection
if (cnn.state = = System.Data.ConnectionState.Open)
{
Cnn.close ();
}
Strerr = "";
Releasing resources
Cnn.dispose ();
Cmd. Dispose ();
Gc. Collect ();
return true;
}
Class State
{
Public FileStream FStream;
public AutoResetEvent autoevent;
Public State (FileStream FStream, AutoResetEvent autoevent)
{
This.fstream = FStream;
This.autoevent = autoevent;
}
}
static void Endwritecallback (IAsyncResult asyncresult)
{
state Stateinfo = (state) asyncresult.asyncstate;
int workerthreads;
int portthreads;
Try
{
Threadpool.getavailablethreads (out WorkerThreads,
Out portthreads);
StateInfo.fStream.EndWrite (asyncresult);
Thread.Sleep (1500);
}
Finally
{
StateInfo.autoEvent.Set ();
}
}
Comparison of two ways:
Mode one: Suitable for large database load, binary data size known;
Mode two: Suitable for the database load is small, binary data size is unknown;
Among them: The asynchronous mechanism of the two methods are the same, without any difference; The advantage of asynchronous mechanism is that it can give full play to the advantages of operating system
Note: Asynchronous mechanisms cannot be used in contexts where performance testing is required, and synchronization mechanisms must be used to improve authenticity
