ThreadStateException在Winform特别是在OpenFileDialog

根据MSDN，发生ThreadStateException主要是因为新线程在主线程中创建了OpenFileDialog的工具;

private void button_FileExercise_Click(object sender, EventArgs e)
{
    OpenFileDialog fileDialog = new OpenFileDialog();
    fileDialog.InitialDirectory = "C:''";
    fileDialog.Filter = "Text Files (*.txt)|*.txt|All Files (*.*)|*.*";
    if (fileDialog.ShowDialog() == DialogResult.OK)
    {
    }
}

ThreadStateException发生在"if"处，因此，我该如何解决这样的程序，谢谢!