Accessing Stream at the same time

Question

I am attempting to reuse the same Stream multiple times. One for resizing the image, and the other for uploading the image. Whilst it does work for resizing the image, it seems to be locking out the other method for uploading the file. I have tried to copy the Stream using Stream.CopyTo(MemoryStream), then using that for uploading, but it still doesn't make a different.

I am opening a Stream using the PhotoChooserTask. I then pass the Stream to a ImageThumbnail method which creates a thumbnail of the image and then saves it to IsolatedStorage as shown below:

    public static void SaveThumbnail(Stream imageStream, string fileName, double imageMaxHeight, double imageMaxWidth)
    {
        var bitmapImage = new BitmapImage();
        bitmapImage.SetSource(imageStream);
        var resizedImage = new WriteableBitmap(bitmapImage);

        using (var isolatedStorage = IsolatedStorageFile.GetUserStoreForApplication())
        {
            double scaleX = 1;
            using (var fileStream = isolatedStorage.CreateFile(fileName))
            {
                //do stuff for resizing here...
                resizedImage.SaveJpeg(fileStream, newWidth1, newHeight1, 0, 100);
            }
        }
    }

At the same time, I am reusing the same Stream from the PhotoChooserTask for uploading the image. EItherway, it seems to be locking eachother out, and no error is being thrown.

Any tips?

score 4 · Accepted Answer · edited May 23 '17 at 12:11

4

You need to copy the stream into a byte array, because streams change during use and can't be cloned.

public static void CopyStream(Stream input, Stream output)
{
    byte[] buffer = new byte[32768];
    while (true)
    {
        int read = input.Read (buffer, 0, buffer.Length);
        if (read <= 0)
            return;
        output.Write (buffer, 0, read);
    }
}

edited May 23 '17 at 12:11

Community

1
1

answered Aug 04 '11 at 15:37

nes1983

15,209
4
44
64

Is that code for Java? Just tried to search for ByteArrayOutputStream class on MSDN, and it's for Java. Would of been really help if it was for C# though. – Daniel Clark Aug 04 '11 at 16:19
Eek, yes, sorry. It's the same for C#, tho: http://stackoverflow.com/questions/2490423/is-it-possible-to-clone-a-net-stream – nes1983 Aug 04 '11 at 16:23
CopyTo is already part of the stream API in .net. I don't see how this answers the original question. – Michael Donohue Aug 04 '11 at 17:47

score 1 · Answer 2 · answered Aug 04 '11 at 17:48

1

Copying to a MemoryStream should do the trick. To reuse the memory stream, you need to reset the position back to the beginning, by setting the Position property back to 0.

answered Aug 04 '11 at 17:48

Michael Donohue

11,776
5
31
44

Accessing Stream at the same time

2 Answers2