Question

I get the following exception when calling saveFileDialog.ShowDialog() in a background thread:

Current thread must be set to single
thread apartment (STA) mode before OLE
calls can be made. Ensure that your
Main function has STAThreadAttribute
marked on it.

According to this:

To fix the problem, insert the
statement:

Threading.Thread.CurrentThread.ApartmentState = Threading.ApartmentState.STA;

in Main right before the
Application.Run statement.

But the Application.Run statement is in Program.cs which seems to be generated code so any changes might be unexpectedly lost. Also, I could not find a way to set current thread to STA in the project or main form properties but maybe I am looking in the wrong place.
What is the proper way to call saveFileDialog.ShowDialog() in a background thread?

Answer 1

ShowDialog() shouldn’t be called from a background thread – use Invoke(..).

Invoke((Action)(() => { saveFileDialog.ShowDialog() }));