function updateDropdown() {
  var ddl = $("#dropdown").data("kendoDropDownList");
  updateDataSourceForDropdown(ddl);
  bnfDropDownList.dataSource.read();
}

function updateDataSourceForDropdown(kendoDropDownList) {
  var dataRequestReadProperty = kendoDropDownList.dataSource.transport.read;
  var requestPayload = getPayload();
  dataRequestReadProperty.data = requestPayload;
}

function getPayload() {
 return {
    key: "value"
  }
}