Invalid Operation Exception - "Cross-thread operation not valid: Control 'TextBox1' accessed from a thread other than the thread it was created on."

Question

"If necessity is the mother of invention, I'd like to kill the guy who invented this."

-Jimmy Buffet

I don't care if 100 people with a million reputation jump down my throat for saying this, but who ever thought of throwing this exception deserves a fate worse than death.

I have QUITE LITERALLY copied and pasted code from one project to another to populate standard data into a small set of text boxes. In one application, the data is displayed perfectly. The new one I'm working on now, throws this exception of course.

So here is my question - why would one throw it and the other not if the code is the same? Is there a setting in the project settings? Is there a property in the text box that prevents this?

I don't recall setting anything in the project to ignore this exception, but the code is EXACTLY THE SAME.

Answer 1

STAThread attribute set on the thread creating the controls?

Is the populating code called in the UI thread or not? Noone cares whether you did copy the code properly - if the call is on the wrong thread to start with.

Answer 2

I don't want to repeat the error message, but you are trying to modify a control from a thread different than th thread that control was created on.

Take a look at InvokeRequired and Invoke.