Problem accessing file from different thread in Asp.net

Question

I have a process in a website (Asp.net 3.5 using Linq-to-Sql for data access) that needs to work as follows:

1. Upload file
2. Record and save info regarding file to database
3. Import data from file into database
4. Redirect to different page

When run sequentially like this, everything works fine. However, since the files being imported can be quite large, I would like step 3 to run on a different thread from the UI thread. The user should get to step 4 while step 3 is still in progress, and the screen on step 4 will periodically update to let the user know when the import is complete.

I am handling the threading as follows:

public class Import {

  public static void ImportPendingFile() {
    Import i = new Import();
    Thread newThread = new Thread(new ThreadStart(i.ImportFile));
    newThread.Start();
  }

  public void ImportFile() {
    // 1. Query DB to identify pending file
    // 2. Open up and parse pending file
    // 3. Import all data from file into DB
    // 4. Update db to reflect that import completed successfully
  }
}

And in the codebehind:

protected void butUpload(object sender, EventArgs e) {
  // Save file, prepare for import
  Import.ImportPendingFile();
  Response.Redirect(NewLocation);
}

When doing this, I am able to confirm via debugger that the new thread is starting up properly. However, whenever I do this, the thread aborts when trying to access the file (step 2 in the code behind). This works fine when run in the main thread, so something about the multi-threaded situation is preventing this. I had thought that since the file is saved to disk (which it is) that there shouldn't be any problem with opening it up in a different thread. Any ideas where I have gone wrong and how I can fix it? Thanks!

Note: I am using a third-party assembly to open the file. Using reflector, I have found the following code related to how it opens up the file:

if (File.Exists(fileName)) {
  using (FileStream stream = new FileStream(fileName, FileMode.Open)) {
    // use stream to open file
  }
}

Answer 1

Try Response.Redirect(url, false) , else the 'Response' will be ended just after that call.

Answer 2

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