DateTimePicker that can set the null value (Nullable)

Since the WinForm DateTimePicker cannot set a null value (NULL), I did an extension based on the original DateTimePicker.

If there is a bug, can feedback, I revise.

usingSystem;usingSystem.ComponentModel;usingSystem.Windows.Forms;namespacewinformtest{ Public classDatetimepicker2:datetimepicker {Const stringNullableformat =" "; BOOLisselfsetting; stringOriginalcustomformat; BOOLoriginalcustomformatinitialized; DateTimePickerFormat?OriginalFormat; BOOLIsnullablestate {Get{return  This. Format = = Datetimepickerformat.custom && This. CustomFormat = =Nullableformat;} }        voidSetnullable (BOOLnullable) {            if(! This. Originalformat.hasvalue) {                 This. OriginalFormat = This.            Format; }            if(! This. originalcustomformatinitialized) {                 This. Originalcustomformat = This.                CustomFormat;  This. originalcustomformatinitialized =true; }             This. isselfsetting =true;  This. Format = nullable? Datetimepickerformat.custom: This. Originalformat.value;  This. CustomFormat = nullable? Nullableformat: This. Originalcustomformat;  This. isselfsetting =false; }        #regionProperties[Browsable (false)] [DesignerSerializationVisibility (Designerserializationvisibility.hidden)] PublicDatetime?Value2 {Get{return  This. Isnullablestate? (DateTime?)NULL: Value;} Set            {                if(value.) HasValue) Value=value.                Value; Setnullable (!value.            HasValue); }        }         Public NewDateTimePickerFormat Format {Get{return Base. Format; }            Set            {                if(! This. isselfsetting) This. OriginalFormat =value; Base. Format =value; }        }         Public New stringCustomFormat {Get{return Base. CustomFormat; }            Set            {                if(! This. isselfsetting) {                     This. Originalcustomformat =value;  This. originalcustomformatinitialized =true; }                Base. CustomFormat =value; }        }        #endregion        #regionEventsprotected Override voidOnGotFocus (EventArgs e) {if( This. isnullablestate) setnullable (false); Base.        OnGotFocus (e); }        protected Override voidOnMouseDown (MouseEventArgs e) {if( This. isnullablestate) setnullable (false); Base.        OnMouseDown (e); }        protected Override voidOnKeyDown (KeyEventArgs e) {setnullable (E.keycode= = Keys.back | | E.keycode = =keys.delete); Base.        OnKeyDown (e); }        #endregion    }}

DateTimePicker that can set the null value (Nullable)