Ext.net RecordField SubmitEmptyValue invalid 无效问题有解决方案吗

< ext:Store 
            ID = " Store1 "  
            runat = " server "  
            AutoSave = " true "  
            ShowWarningOnFailure = " false "
            OnBeforeStoreChanged = " HandleChanges "  
            SkipIdForNewRecords = " false "
            RefreshAfterSaving = " None " >
             < Reader >
                 < ext:JsonReader IDProperty = " Id " >
                     < Fields >
                         < ext:RecordField Name = " Id "   / >
                         < ext:RecordField Name = " Email "  AllowBlank = " false "   / >
                         < ext:RecordField Name = " First "  AllowBlank = " true "   SubmitEmptyValue = " Null "   / >
                         < ext:RecordField Name = " Last "  AllowBlank = " true "   SubmitEmptyValue = " Undefined "   / >
                     < / Fields>
                 < / ext:JsonReader>
             < / Reader>
            
             < Listeners >
                 < Exception Handler = "
                    Ext.net.Notification.show({
                        iconCls    : 'icon-exclamation', 
                        html       : e.message, 
                        title      : 'EXCEPTION', 
                        autoScroll : true, 
                        hideDelay  : 5000, 
                        width      : 300, 
                        height     : 200
                    }); "   / >
                 < BeforeSave Handler = " var valid = true; this.each(function(r){if(r.dirty && !r.isValid()){valid=false;}}); return valid; "   / >
             < / Listeners>
         < / ext:Store>

  <ext:FormPanel 

            ID = " UserForm "  
            runat = " server "
            Icon = " User "
            Frame = " true "
            LabelAlign = " Right "
            Title = " User -- All fields are required "
            Width = " 500 " >
             < Items >
                 < ext:TextField runat = " server "
                    FieldLabel = " Email "
                    DataIndex = " Email "
                    AllowBlank = " false "
                    Vtype = " email "
                    AnchorHorizontal = " 100% "
                     />
                
                 < ext:TextField runat = " server "
                    FieldLabel = " First "
                    DataIndex = " First "
                    AllowBlank = " true "
                    AnchorHorizontal = " 100% "
                     />
                
                 < ext:TextField runat = " server "
                    FieldLabel = " Last "
                    DataIndex = " Last "
                    AllowBlank = " true "
                    AnchorHorizontal = " 100% "
                     />
             </ Items >
            
             < Buttons >
                 < ext:Button 
                    runat = " server "
                    Text = " Save "
                    Icon = " Disk " >
                     < Listeners >
                         < Click Handler = " updateRecord(#{UserForm}); "   />
                     </ Listeners >
                 </ ext:Button >
                
                 < ext:Button 
                    runat = " server "
                    Text = " Create "
                    Icon = " UserAdd " >
                     < Listeners >
                         < Click Handler = " addRecord(#{UserForm}, #{GridPanel1}); "   />
                     </ Listeners >
                 </ ext:Button >
                
                 < ext:Button 
                    runat = " server "
                    Text = " Reset " >
                     < Listeners >
                         < Click Handler = " #{UserForm}.getForm().reset(); "   />
                     </ Listeners >
                 </ ext:Button >
             </ Buttons >
         </ ext:FormPanel >

---

 我将

SubmitEmptyValue = " Null " 和”Undefined“ 都试过了，当输入空值，也就是TextBox空白的情况后台对应的 

First，Last字段的值是StringEmpty，并不是NULL，这让我很头疼，那位大侠做过类似的项目，不知道是否有解决方案。