BitmapFrame in another thread
- by Lasse Lindström
Hi
I am using a WPF BackgroundWorker to create thumbnails. My worker function looks like:
private void work(object sender, DoWorkEventArgs e)
{
try
{
var paths = e.Argument as string[];
var boxList = new List();
foreach (string path in paths)
{
if (!string.IsNullOrEmpty(path))
{
FileInfo info = new FileInfo(path);
if (info.Exists && info.Length 0)
{
BitmapImage bi = new BitmapImage();
bi.BeginInit();
bi.DecodePixelWidth = 200;
bi.CacheOption = BitmapCacheOption.OnLoad;
bi.UriSource = new Uri(info.FullName);
bi.EndInit();
var item = new BoxItem();
item.FilePath = path;
MemoryStream ms = new MemoryStream();
PngBitmapEncoder encoder = new PngBitmapEncoder();
encoder.Frames.Add(BitmapFrame.Create(bi));
encoder.Save(ms);
item.ThumbNail = ms.ToArray();
ms.Close();
boxList.Add(item);
}
}
}
e.Result = boxList;
}
catch (Exception ex)
{
//nerver comes here
}
}
When this fuction is finnished and before the BackgroundWorker "Completed" function is started, I can see on the output window on Vs2008, that a exception is generated. It looks like:
A first chance exception of type 'System.NotSupportedException' occurred in PresentationCore.dll
The number of exceptions generates equals the number of thumbnails to be generated.
Using "trial and error" I have isolated the problem to:
BitmapFrame.Create(bi)
Removing that line (makes my function useless) also removes the exception.
I have not found any explanation to this,,, or a better method to create thumbnails i a background thread.
Can anyone help me?
//lasse
