Question

i have a class which, when a certain part of the gui is clicked will

-create a backgroundworker and do the following taks

-create a new object(this is a new windows form)

-call a method on it which gets some data

-populate the new windows form gui with that data

The problem is there is a gui component on the form which cant be created from outside of the main programme thread, if i do try i get the error

Active x …. cannot be instantiated because the
current thread is not in a
single-threaded apartment.

is there help people can offer so i can structure this?

in my do work

Answer 1

Don’t create GUI components in a background thread. Use the background thread to get and process data, then render them in the UI in the main thread. I know that this in inconvenient, because

• creating lots of UI elements can also take a lot of time and
• creating them in the UI thread requires you to split your code into UI part and data processing part,

but there’s not really a way around it. .NET UI components are not designed to be handled in background threads.

To perform only certain operations of your code in the main thread, you can use

• someUIControl.Invoke(...) (WinForms) or
• Dispatcher.Invoke(...) (WPF)

in the DoWork event handler of your BackgroundWorker. Alternatively, you can perform the UI operations in the RunWorkerCompleted event handler of your BackgroundWorker, which always executes in the UI thread.