[wpf] The calling thread must be STA, because many UI components require this

I am using http://www.codeproject.com/KB/IP/Facebook_API.aspx

I am trying to call the XAML which is created using WPF. But it gives me an error:

The calling thread must be STA, because many UI components require this.

I don't know what to do. I am trying to do this:

FacebookApplication.FacebookFriendsList ffl = new FacebookFriendsList();

But it is giving me that error.

I added a background worker:

static BackgroundWorker bw = new BackgroundWorker();

static void Main(string[] args)
{
    bw.DoWork += bw_DoWork;
    bw.RunWorkerAsync("Message to worker");
    Console.ReadLine();
}

static void bw_DoWork(object sender, DoWorkEventArgs e)
{
    // This is called on the worker thread
    FacebookApplication.FacebookFriendsList ffl = new FacebookFriendsList();

    Console.WriteLine(e.Argument);        // Writes "Message to worker"

    // Perform time-consuming task...
}

If the Application.Current is null for example by unit test, you can try this:

 System.Windows.Threading.Dispatcher.CurrentDispatcher.Invoke( YOUR action )

Just mark your program with the [STAThread] attribute and the error goes away! it's magic :)

For me, this error occurred because of a null parameter being passed. Checking the variable values fixed my issue without having to change the code. I used BackgroundWorker.

Try to invoke your code from the dispatcher:

Application.Current.Dispatcher.Invoke((Action)delegate{
      // your code
});

I suspect that you are getting a callback to a UI component from a background thread. I recommend that you make that call using a BackgroundWorker as this is UI thread aware.

For the BackgroundWorker, the main program should be marked as [STAThread].

If you call a new window UI statement in an existing thread, it throws an error. Instead of that create a new thread inside the main thread and write the window UI statement in the new child thread.

If you make the call from the main thread, you must add the STAThread attribute to the Main method, as stated in the previous answer.

If you use a separate thread, it needs to be in a STA (single-threaded apartment), which is not the case for background worker threads. You have to create the thread yourself, like this:

Thread t = new Thread(ThreadProc);
t.SetApartmentState(ApartmentState.STA);

t.Start();

with ThreadProc being a delegate of type ThreadStart.

You can also try this

// create a thread  
Thread newWindowThread = new Thread(new ThreadStart(() =>  
{  
    // create and show the window
    FaxImageLoad obj = new FaxImageLoad(destination);  
    obj.Show();  
    
    // start the Dispatcher processing  
    System.Windows.Threading.Dispatcher.Run();  
}));  

// set the apartment state  
newWindowThread.SetApartmentState(ApartmentState.STA);  

// make the thread a background thread  
newWindowThread.IsBackground = true;  

// start the thread  
newWindowThread.Start();