Accessing UI (Main) Thread safely in WPF

Question

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.

Answer 1

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 */ }));