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.NET Forum / Windows Forms / WinForm General / July 2007Reading file associated icons from a secondary thread not returning correct icon - IconTest.zip (0/1)
I need to read the icons from a secondary thread so that the file list is returned prompty in a listview. I'm using a background worker object to retrieve icons asynchronously. What happens is that the icons for certain files (I verified this happens for xml and sln files on my system) are not correctly retrieved (I get the standard blank icon). I'm attaching a sample application that retrieves the icons synchronously and asynchronously. Thanks Andrea Hi Andrea, I run your sample application and do see the problem on my side. When I click the 'Read Async' button and navigate to a folder that contains a .sln and a .xml files, the associated icons to the two files are the standard blank icon. However, when I click the 'Read Sync' button and navigate to the same folder, the associated icons to the two files are correct. I notice that when the application gets the associated icon asynchronous using the SHGetFileInfo function, the returned iIcon memeber of the structure specified by the psfi is of value 0, which is not correct. public static Icon GetAssociatedIcon(string strPath, bool smallIcon) { .... int result = SHGetFileInfo(strPath, 0, out info, (uint)cbFileInfo, flags); if (info.hIcon != IntPtr.Zero) { retIcon = Icon.FromHandle(info.hIcon); // when the SHGetFileInfo function is called by a thread other than the UI thread, the info.iIcon memeber returns 0, which is not correct int index = info.iIcon; } return retIcon; } I will go on the research and get the result back to you ASAP. I appreciate your patience! Sincerely, Linda Liu Microsoft Online Community Support ================================================== Get notification to my posts through email? Please refer to http://msdn.microsoft.com/subscriptions/managednewsgroups/default.aspx#notif ications. Note: The MSDN Managed Newsgroup support offering is for non-urgent issues where an initial response from the community or a Microsoft Support Engineer within 1 business day is acceptable. Please note that each follow up response may take approximately 2 business days as the support professional working with you may need further investigation to reach the most efficient resolution. The offering is not appropriate for situations that require urgent, real-time or phone-based interactions or complex project analysis and dump analysis issues. Issues of this nature are best handled working with a dedicated Microsoft Support Engineer by contacting Microsoft Customer Support Services (CSS) at http://msdn.microsoft.com/subscriptions/support/default.aspx. ================================================== This posting is provided "AS IS" with no warranties, and confers no rights. Thanks Linda. Hope there's a way to get the icons from a secondary thread so that I can display the items in the list first and then load the icons. Thanks so much for your help. Andrea >Hi Andrea, > [quoted text clipped - 56 lines] > >This posting is provided "AS IS" with no warranties, and confers no rights. Have you got any news for me, Linda? Thanks Andrea >Hi Andrea, > [quoted text clipped - 56 lines] > >This posting is provided "AS IS" with no warranties, and confers no rights. Hi Andrea, Sorry for my delayed response. I was OOF yesterday. I discussed this problem with my workmate. We found that the problem exists only when the ApartmentState is set to MTA. If you comment out the STAThreadAttribute on the static Main method, you should see that you can't get the correct icons for .sln and .xml files even when you click the 'Read Sync' button. So the workaround to this problem is to set the ApartmentState of the thread that the BackgroundWorker uses to STA. Unfortunately, I haven't worked out how to do it until now. Alternatively, you may create a Thread and set the thread's ApartmentState to STA. The following is a sample. private void AddIcons() { .... DisplayIcon(); } delegate void ShowIconDelegate(); private void DisplayIcon() { if (this.InvokeRequired) { this.Invoke(new ShowIconDelegate(DisplayIcon)); } else { int cont = 0; for (; cont < this.iconlistAsync.Count; cont++) { this.imageListAsync.Images.Add(iconlistAsync[cont]); listViewAsync.Items[cont].ImageIndex = cont; DestroyIcon(iconlistAsync[cont].Handle); } } } private void btnReadAsync_Click(object sender, EventArgs e) { .... //backgroundWorker1.RunWorkerAsync(); Thread thd = new Thread(new ThreadStart(AddIcons)); thd.TrySetApartmentState(ApartmentState.STA); thd.Start(); } Hope this helps. Sincerely, Linda Liu Microsoft Online Community Support Thanks so much Linda. You are really an asset for this newsgroup. I tried your solution and it worked like a charm. I wonder if I could use a thread pool to simultaneously load more icons to speed things up a little bit more. However, it's already a big improvement. Thanks. Andrea >Hi Andrea, > [quoted text clipped - 53 lines] >Linda Liu >Microsoft Online Community Support Hi Andrea, Thank you for your feedback. Thread pooling is not compatible with the single-threaded apartment (STA) model. However, in your scenario, the thread must to be set to the STA mode. So it's impossible to use thread pooling in your application. Hope this helps. If you have any other concerns, please feel free to let me know. Sincerely, Linda Liu Microsoft Online Community Support Hi Andrea, How about the problem now? If you have any question, please feel free to let me know. Thank you for using our MSDN Managed Newsgroup Support Service! Sincerely, Linda Liu Microsoft Online Community Support Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. 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