wpf - C# ListBox not showing added items when added from DispatcherTimer.Tick -

this looks weird behaviour me , since not blame else myself spent hours trying fix - not understand @ all:

i noticed problem occures in method called dispatchertimer.tick event. multi-thread issue.

1. i have listbox:

   <listbox itemssource="{binding configurationerrors, mode=oneway}"/> 

2. it binds to:

   private observablecollection<string> _configurationerrors = new observablecollection<string>();  public observablecollection<string> configurationerrors {     {         return _configurationerrors;     } }  /// <summary> ///     adds configuration error window. /// </summary> /// <param name="errormessage">the message add.</param> public void addconfigurationerror(string errormessage) {     if(string.isnullorempty(errormessage))         return;      _configurationerrors.add(errormessage);     notifypropertychanged("configurationerrors"); }  /// <summary> ///     removes configuration errors window. /// </summary> public void clearconfigurationerrors() {     _configurationerrors.clear();     notifypropertychanged("configurationerrors"); } 

addconfigurationerror(string errormessage) sucessfully adds message if called
from anywhere in mainwindow.
(from constructor , anywhere else)

3. and have looping method (called dispatchertimer.tick) in instance stored in app.cs, contains following code:

       //file exists     if (configfilepath == null) {         _mainwindow.addconfigurationerror("could not retrieve config filepath.");         throw new invaliddataexception("could not retrieve config filepath.");     } else if (!file.exists(configfilepath)) {         _mainwindow.addconfigurationerror("could not find config. (" + configfilepath + ")");         throw new invaliddataexception("could not find config. (" + configfilepath + ")");     } 

the exceptions being thrown , addconfigurationerror() being called. can log message passed addconfigurationerror() , works, - control not recieve binding update.

is because dispatchertimer.tick runs in different thread , bindings may not work expected way wrote it? , how can fix it?

thank in advance.

call methods on proper mainwindow instance. haven't shown how create _mainwindow, instead of calling

_mainwindow.addconfigurationerror(...); 

you should call

((mainwindow)application.current.mainwindow).addconfigurationerror(...);