UWP/C# - How can I wait for a file to appear before reading it?-CodePudding

I am writing to a file, then reading it back right after:

await FileIO.WriteTextAsync(file, command, Windows.Storage.Streams.UnicodeEncoding.Utf8);   
var readFile = await ApplicationData.Current.TemporaryFolder.GetFileAsync(WEB_LOG);

However, GetFileAsync throws a FileNotFoundException because the file hasn't appeared yet. If I use the debugger and wait a little after WriteTextAsync finishes, I can see the file appear in the folder and GetFileAsync does not throw an exception. How can I wait for the file to be fully written to and appear in the folder so that GetFileAsync does not throw an exception?

CodePudding user response：

You could try to use StorageFolder.TryGetItemAsync(String) to check if the file is ready. This method returns null instead of raising a FileNotFoundException if the specified file or folder is not found.

Like this:

 var target=  await ApplicationData.Current.TemporaryFolder.TryGetItemAsync("FileName");

        if (target != null)
        {
            // file is ready
        }
        else 
        {
            //wait and try to get the file again
        }

CodePudding user response：

There is no function, which will allow you to wait on a particular file to be available for reading. You have to check if it is not ready then wait...

 await FileIO.WriteTextAsync(file, command, Windows.Storage.Streams.UnicodeEncoding.Utf8); 

        while (true)
        {
            try
            {
                using (FileStream inputStream = File.Open(filename, FileMode.Open, FileAccess.Read, FileShare.None))
                    if (inputStream.Length > 0)
                        break;
            }
            catch (Exception)
            {
                await Task.Delay(50);
            }
        }

var readFile = await ApplicationData.Current.TemporaryFolder.GetFileAsync(WEB_LOG);