javascript - Why does the Kendo TreeView delete nodes after drag and drop? -

i have kendo treeview bound datasource connected crud api via transport object.

i want re-order nodes in tree using drag , drop , save these changes db.

i calling .sync() on datasource in dragend event handler of treeview.

var commandstreeview = $("#commandgroups-treeview").kendotreeview({     datasource: mydatasource,     draganddrop: true,     dragend: function(e) {         // sync changes db         mydatasource.sync(); } 

});

however create 2 ajax calls:

1. put updates
2. deleteon node has been dragged , dropped.

in api react on changes in put request , re-organize object relations in tha database object gets deleted afterwards.

this bad in database there bunch of other tables have foreign keys on object , deleted on cascade, well.

this confusing me.

1. why dragged object deleted?
2. how can prevent happening?

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edit: here's workaround

1. gather information need service
2. calling service manually
3. remember nodes expanded
4. cancel changes kendo stored in datasource
5. re-read data service (the data has been manupulated drag , drop service call earlier, reflects new order already)
6. re-expand remembered nodes, read call close tree nodes

some code

//…          dragend: function(e) {      var draganddropdata = {};     draganddropdata.dropposition = e.dropposition;     draganddropdata.sourcenode = json.parse(kendo.stringify(mydatasource.getbyuid($(e.sourcenode).attr('data-uid'))));     draganddropdata.destinationnode = json.parse(kendo.stringify(mydatasource.getbyuid($(e.destinationnode).attr('data-uid'))));      $.ajax({         url: myserviceurl,         type: 'get',         datatype: 'html',         contenttype: "application/json",         data: draganddropdata     })     .done(function(data) {         // remember expanded nodes         var expandeditemsids = [];         commandstreeview.element.find(".k-item").each(function (index, value) {             var item = commandstreeview.dataitem(this);             if (item.expanded) {                 expandeditemsids.push( item.id );             }         });          // cancel kendo widget has done wrong         // e.g. wrong indexes or items marked delete         mydatasource.cancelchanges();          // re-read (correct) data server         var promise = mydatasource.read();          // reset expanded nodes         promise.done(function() {             $(expandeditemsids).each(function(index, value) {                 var nodetoexpand = commandstreeview.findbyuid(mydatasource.get(value).uid);                 commandstreeview.expand(nodetoexpand);             });         });      })  }