CODEWITHSUNDEEP
c#wpf
ScottinTexas
ScottinTexas

Reputation: 181

How do I pass a file back from the FileSystemWatcher WPF C#

WPF Application, C#, MVVM pattern.

My application watches a folder on the network. When a file gets created in that folder I want to parse the data from the file and store the parsed information in a collection. Then move the original file to another folder on the network. My problem is that I cannot move the parsed file from the thread watching the folder to the thread with the collection and the UI. My latest attempt was to try a delegate, but I don't think I have that right. 

    private ObservableCollection<TestFile> destinationFiles=new ObservableCollection<TestFile>();
        public string DestinationFolder
        {
            get { return destinationFolder; }
            set
            {
                if (destinationFolder != value)
                {
                    destinationFolder = value;
                    UpdateFileList("Destination");
                }
                RaisePropertyChanged();
            }
        }

    public MainWindowViewModel()
    {
        watcher.NotifyFilter = NotifyFilters.LastWrite;
        watcher.Created += new FileSystemEventHandler(OnCreated);
        watcher.Changed += new FileSystemEventHandler(OnChanged);  
    }


    public delegate void GetFileDelegate(string str);
    public void OnCreated(object sender, FileSystemEventArgs e)
    {
        string name = e.FullPath;
        GetFileDelegate del = new GetFileDelegate(GetFile);
        Dispatcher.CurrentDispatcher.Invoke(del, name);
    }

    public void GetFile(string name)
    {

        TestFile tst = new TestFile(name);
        FileName = name;

        DestinationFiles.Add(tst); //Here is the exception!

    }

The mainwindowviewmodel sets up the FileSystemWatcher. Code for selecting folders and all of that has been left out for brevity, but the constructor is complete as shown.

This runs to the point of updating the Collection: DestinationFiles.Add(tst). Here the exception is thrown for trying to update the collection from a thread different from the Dispatcher thread.

The FileSystemWatcher does not have a "ReportProgress" method as the Background worker has. So I cannot pass back the file through that. I have found a few "examples" showing how to update the UI from the FileSystemWatcher. None found were newer than 2012. Those found did not include code examples that would compile. Others found ignored the WPF and MVVM part of the search string.

Upvotes: 0

Views: 769

Answers (2)

Rekshino
Rekshino

Reputation: 7325

Use Application.Current.Dispatcher instead of Dispatcher.CurrentDispatcher See the difference: Dispatcher.CurrentDispatcher vs. Application.Current.Dispatcher

Upvotes: 1

Amittai Shapira
Amittai Shapira

Reputation: 3827

When you call Dispatcher.CurrentDispatcher you're using the current worker thread. In order to make the call on the UI thread in WPF you should use instead:

Application.Current.Dispatcher.Invoke(del, name);

Upvotes: 0

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