<style type="text/css">
    .k-master-row td {
      overflow: visible !important;
    }
  </style>

buttonGroup.badge(index, false);

 <button id="button" type="button">Submit</button>
 <script>
     $("#button").kendoButton({
         click: function (e) {
             //alert(combobox.value);
             //alert(e.event.target.tagName);

             var dataSource = new kendo.data.DataSource({
                 transport: {
                     // make JSONP request to https://demos.telerik.com/kendo-ui/service/products/create
                     create: {
                         url: "https://localhost:7170/api/Kunden",
                         dataType: "json", // "jsonp" is required for cross-domain requests; use "json" for same-domain requests
                         type: "PUT"
                     },
                     parameterMap: function (data, type) {
                         if (type == "create") {
                             // send the created data items as the "models" service parameter encoded in JSON
                             return { models: kendo.stringify(data.models) };
                         }
                     }
                 },
                 schema: {
                     model: {
                         id: "kundenId", // the identifier of the model
                         fields: {
                             id: { editable: false, nullable: true },
                         }
                     }
                 }
             });
             // create a new data item
             dataSource.add({ id: 4713 });
             //dataSource.insert(0, { id: 4714 });
             // save the created data item
             dataSource.sync(); // server response is [{"ProductID":78,"ProductName":"New Product","UnitPrice":0,"UnitsInStock":0,"Discontinued":false}]
             //dataSource.pushCreate([{ id: combobox.value }]);
         }
     });
 </script>

namespace Api.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class KundenController : ControllerBase
    {
        // GET: api/Kunden
        [HttpGet]
        public async Task<ActionResult<IEnumerable<Kunde>>> GetKundeItems()
        {
            //return await _context.KundeItems.ToListAsync();
            DataAccess dataAccess = new DataAccess();
            return dataAccess.GetKunden();
        }

        // GET: api/Kunden/5
        [HttpGet("{id}")]
        public async Task<ActionResult<Kunde>> GetKunde(long id)
        {
            //var kunde = await _context.KundeItems.FindAsync(id);
            DataAccess dataAccess = new DataAccess();
            Kunde kunde = dataAccess.GetKunde(id);
            if (kunde == null)
            {
                return NotFound();
            }

            return kunde;
        }


        // PUT: api/Kunden/5
        [HttpPut]
        public async Task<ActionResult<Kunde>> SetKunde(KundeShort kdn)
        {
                return NotFound();
        }
   }
}