Accessing UI (Main) Thread safely in WPF
.net, c#, datagrid, multithreading, wpf
Solution
You can use
`Dispatcher.Invoke(Delegate, object[])`
on the `Application`'s (or any `UIElement`'s) dispatcher.
You can use it for example like this:
Application.Current.Dispatcher.Invoke(new Action(() => { /* Your code here */ }));
or
someControl.Dispatcher.Invoke(new Action(() => { /* Your code here */ }));
Problem
I have an application which updates my datagrid each time a log file that I'm watching gets updated (Appended with new text) in the following manner: ``` private void DGAddRow(string name, FunctionType ft) { ASCIIEncoding ascii = new ASCIIEncoding(); CommDGDataSource ds = new CommDGDataSource(); int position = 0; string[] data_split = ft.Data.Split(' '); foreach (AttributeType at in ft.Types) { if (at.IsAddress) { ds.Source = HexString2Ascii(data_split[position]); ds.Destination = HexString2Ascii(data_split[position+1]); break; } else { position += at.Size; } } ds.Protocol = name; ds.Number = rowCount; ds.Data = ft.Data; ds.Time = ft.Time; dataGridRows.Add(ds); rowCount++; } ... private void FileSystemWatcher() { FileSystemWatcher watcher = new FileSystemWatcher(Environment.CurrentDirectory); watcher.Filter = syslogPath; watcher.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite | NotifyFilters.FileName | NotifyFilters.DirectoryName; watcher.Changed += new FileSystemEventHandler(watcher_Changed); watcher.EnableRaisingEvents = true; } private void watcher_Changed(object sender, FileSystemEventArgs e) { if (File.Exists(syslogPath)) { string line = GetLine(syslogPath,currentLine); foreach (CommRuleParser crp in crpList) { FunctionType ft = new FunctionType(); if (crp.ParseLine(line, out ft)) { DGAddRow(crp.Protocol, ft); } } currentLine++; } else MessageBox.Show(UIConstant.COMM_SYSLOG_NON_EXIST_WARNING); } ``` When the event is raised for the FileWatcher, because it creates a separate thread, when I try to run dataGridRows.Add(ds); to add the new row, the program just crashes without any warning given during debug mode. In Winforms, this was easily solved by utilizing the Invoke function but I am not sure how to go about this in WPF.