Decrements the value of the spin box (also known as an up-down control).
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
When the method is called, either in code or by the click of the down button, the new value is validated and the control is updated with the new value in the appropriate format. Specifically, if the UserEdit property is set to true, the ParseEditText method is called prior to validating or updating the value. The value is then validated to be between the Minimum and Maximum values, and the UpdateEditText method is called.