In this particular case, we are using the SetToNullValue() method. To reproduce this behavior we can type a valid date in the editor area. Press the tab key to move the focus out of the control. Call the SetToNullValue() method which will set the Value property to null. Focus again on the control and type the same date again. When we tab out of the control, the date is valid and will be shown in the editor area. However, the Value property remains empty.