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

Question

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

User · Answer

Just mark your program with the  STAThread  attribute and the error goes away  it s magic

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

If the Application Current is null for example by unit test  you can try this   System Windows Threading Dispatcher CurrentDispatcher Invoke  YOUR action

User · Answer

You can also try this    create a thread   Thread newWindowThread   new Thread new ThreadStart      gt               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

User · Answer

Try to invoke your code from the dispatcher   Application Current Dispatcher Invoke  Action delegate           your code

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

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