FileIO in win 8 app

Question

I have to log my application events and exceptions in a file in win 8 app in documents folder

Windows.Storage.StorageFolder localFolder = KnownFolders.DocumentsLibrary;

The problem is when I call WriteToFile function one after other there is an access is denied exception because the file is still being used. Is there a way to make this work

public async void WriteToFile(string log)
            {
                try
                {

                    StorageFile sampleFile = await localFolder.CreateFileAsync("dataFile.txt", CreationCollisionOption.OpenIfExists);
                    //StorageFile sampleFile = await localFolder.GetFileAsync("dataFile.txt");
                    IRandomAccessStream writeStream = await sampleFile.OpenAsync(FileAccessMode.ReadWrite);
                    IOutputStream outputStream = writeStream.GetOutputStreamAt(writeStream.Size);
                    DataWriter dataWriter = new DataWriter(outputStream);
                    dataWriter.WriteString(log);

                    dataWriter.StoreAsync().AsTask().Wait();
                    outputStream.FlushAsync().AsTask().Wait();

                }
                finally
                {

                }

            }

score 2 · Answer 1 · edited May 23 '17 at 10:34

2

Looks like you forgot to close the Stream after write operation. The file will be locked until you close the Stream.

dataWriter.Close();

MSDN Link

or use the "using" Keyword like this:

 using(DataWriter dataWriter = new DataWriter(outputStream)) 
 {
       dataWriter.WriteString(log);
       dataWriter.StoreAsync().AsTask().Wait(); 
 }

It's a good idea to check if the file is locked, so you didn't get an exception.

How to Check for locked file

Greetings, hope it helps

edited May 23 '17 at 10:34

Community

1
1

answered Aug 22 '12 at 12:02

Verni

211
1
9

Tried this but still the same I guess will need to queue all the tasks. – CognitiveDesire Aug 23 '12 at 09:08
Yea, parallel access to file is complicated. It's easier with a serial access :) – Verni Aug 27 '12 at 13:39

score 0 · Answer 2 · answered Aug 22 '12 at 12:50

0

you could try the following

dataWriter.Dispose();
await outputStream.FlushAsync();
await stream.FlushAsync();

answered Aug 22 '12 at 12:50

alfah

2,077
1
31
55

Tried this but still the same I guess will need to queue all the tasks. – CognitiveDesire Aug 23 '12 at 09:11

FileIO in win 8 app

2 Answers2