Question

I believe I have found a bug, when the focus is on a TextBox control and I press "Enter" the form will be closed immediately. It means that when I have entered something into a textbox and press "Enter" the focus will not move the next control but close the form.

Answer

This is standard behaivor for the TextBox control. To override this you have to change the ReturnAsTab property from False to True. This will tell the text box to tab to the next control instead of closing the dialog box, as is the default behaivor.