Set a form to “autosize” allows the form to shrink or grow by it’s contents. It however does not allow the user to resize the form manually.
To allow the user to resize the form set the form AutoSize property to false in the form onLoad event handler. This allows the form resize initially but user resizable afterwards.
Of course changing the contents of the hosted controls may require you to resize the form. You can set the AutoSize to true before making the changes or use the GetPreferredSize method and resize the form yourself.