file io - Cross-thread operation not valid: Control accessed from a thread other than the thread it was created on

Question

I am writing a filewatcher windows application which will look for changes in a specified folder and then logs the details in a txt file.

I followed exactly what is mentioned in this article below http://www.codeproject.com/KB/dotnet/folderwatcher.aspx

When I hit F5 from my application and then create or modify a file in the folder that is being watched it throws the below mentioned error.

Please help

Cross-thread operation not valid: Control 'txtFolderActivity' accessed from a thread other than the thread it was created on.

Answer 1

You have to use the Invoke method on the form e.g. with an anonymous delegate to make your changes in reaction to the event.

The event handler is raised with another thread. This 2nd thread cannot access controls in your form. It has to "Invoke" them to let the thread do all control work that initially created them.

Instead of:

myForm.Control1.Text = "newText";

you have to write:

myForm.Invoke(new Action(
delegate()
{
  myForm.Control1.Text = "newText";
}));