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Khalid Mushtaq
NA
7
18.2k
Application Not Respoding while BackgroundWorker Thread Working...
Sep 21 2010 6:56 AM
HI,
I am using BackgroundWorker in scanning a document using C#.NET.
The problem is that while I call the BackgroundWorker.RunWorkerAsync() method, application doesn't respond. After finishing the do work it start responding again. As I know BackgroundWorker thread is used to work at background while user can do work in main UI thread... Please make me correct if i am wrong.
Here is the BackgroundWorker code.
BackgroundWorker backWorker = new BackgroundWorker();
backWorker.WorkerReportsProgress = true;
backWorker.DoWork += new DoWorkEventHandler(backWorker_DoWork);
backWorker.ProgressChanged += new ProgressChangedEventHandler(backWorker_ProgressChanged);
backWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backWorker_RunWorkerCompleted);
progressBar.Visible = true;
backWorker.RunWorkerAsync();
}
private void backWorker_DoWork(object sender, DoWorkEventArgs e)
{
try
{
List<Bitmap> docs = new List<Bitmap>();
string currFilename;
// Create a scanner instance (the user can select if more than one)
ItemClass scanner = (ItemClass)wiaManager.Create(ref missing);
// Show the standard scanning dialog (this is not a required step...)
CollectionClass scans = scanner.GetItemsFromUI(
WiaFlag.SingleImage, WiaIntent.ImageTypeText)
as CollectionClass;
// If the user clicks Cancel, collection is NULL
if (scans != null && scans.Count > 0)
{
// Transfer any scanned pictures to disk
ItemClass scan;
foreach (object wiaObj in scans)
{
scan = (ItemClass)Marshal.CreateWrapperOfType(wiaObj, typeof(ItemClass));
// create temporary file for image
currFilename = Path.GetTempFileName();
// transfer picture to our temporary file
scan.Transfer(currFilename, false);
// Create a Bitmap from the loaded file (Image.FromFile locks the file...)
using (FileStream fs = new FileStream(currFilename, FileMode.Open, FileAccess.Read))
{
// KLUDGE: Must wrap the FromStream Image with a new Bitmap.
// Otherwise get OutOfMemoryException later when using ColorMatrix on it.
docs.Add(new Bitmap(Image.FromStream(fs)));
fs.Close();
}
// Don't leave junk behind!
File.Delete(currFilename);
if (docs.Count > 0)
OpenImage(docs[0]);
}
}
}
catch (Exception ex)
{
MessageBox.Show(string.Format("Sorry, image did not scan. Please try again.\n{0}", ex.Message), "Scanner error");
}
}
private void backWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
progressBar.Value = e.ProgressPercentage;
}
private void backWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
progressBar.Visible = false;
backWorker.ReportProgress(0);
}
The time where application is not responding to user is while executing the code that I have made bold
// transfer picture to our temporary file
scan.Transfer(currFilename, false);
The output is always ok. I just need to make application respond while scanning document at background.
Please help me if you can.
Thanks in advance.
Reply
Answers (
6
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