The SubmitButton control will cause a submission of the form that it is in back to the server. Unlike callbacks that are set up using handlers or the On function, this will cause the Compose function to run each time the button is pressed. Because the class has two public fields with the same name as the EditFields created below, MiServer will populate these two variables with the input each time the form is posted back.

Today, this type of page, which refreshes completely each time the button is pressed, is considerd old-fashioned: new applications should use AJAX-style interation, as do the vast majority of the MS3 samples.