When using aggregates, it should be possible to define your own aggregate function, or even set it globally for kendo, so it could be used in other places. i.e. 

currently you can only specify the function name like 'sum', 'avg', etc. with this idea you could give the whole function like function(arguments...) {}

Also from what I saw it would be nice to have the `functions` object from kendo.data.js accessible, so you could add your custom functions, like:
`kendo.data.aggregate_functions['median'] = function(arguments...) {}` 

At the moment, the DataSource only uses one field for its ID property (if you enter several, then only one is used, apparently).  This doesn't reflect reality, in that in many cases (where one record is a child of another), the key field for a database table is a composite (from 2 or more fields).  
The existing situation causes problems in inline editing of the KendoUI grid, because default values need to be set for foreign key fields, but if these are set to a valid value, then spurious calls to the Inline_Create method occur because the DataSource treats the record as a new record when it is not.
In any case, allowing multiple fields would simply reflect reality.

This is more of a feature request...

If I want to refresh a datasource every 60 seconds, be it a grid, a dropdown, etc., I have to add a snippet of code something like this:

var interval = 60000;

         setInterval(function()

         {
             $("#my-grid").data("kendoGrid").dataSource.read();
         }, interval);

Yes, I realize this is trivial, but it would be nice if you could add an AutoRefresh function directly to the DataSource API that handled all of this under the covers.  Example:

This feature was already requested in another post, but it was missunderstood. (http://kendoui-feedback.telerik.com/forums/127393-kendo-ui-feedback/suggestions/11578722-support-sorting-datasource-groups)

The idea is to allow for Groups in DataSources to be sorted in ways other than alphabetically; this will allow for certain groups to be given priority.

We use the new version of SignalR which is 2.2.3 currently and it seems the Kendo DataSource cannot bind to it. It would be awesome if Kendo supported it. 
Here is a link: https://www.nuget.org/packages/Microsoft.AspNet.SignalR.Core/

http://odata.github.io/WebApi/#04-26-InOperator

OData v4 now supports the IN operator as a short hand for multiple or queries (as of http://docs.oasis-open.org/odata/new-in-odata/v4.01/cn01/new-in-odata-v4.01-cn01.html#_Toc485385090 ). This could help to change code such as:

var selectedStations = $("#cmbStations").data("kendoMultiSelect").dataItems();
            var stationIds = [];
            for (var i = 0; i < selectedStations.length; i++) {
                stationIds.push({
                    field: "StationId",
                    operator: "eq",
                    value: stationId
                });
            }
            dataSource.filter({
                logic: "or",
                filters: stationIds
            });

into a much cleaner:

var selectedStations = $("#cmbStations").data("kendoMultiSelect").dataItems();
            var stationIds = [];
            for (var i = 0; i < selectedStations.length; i++) {
                stationIds.push(selectedStations[i].StationId);
            }
            dataSource.filter({
                field: "StationId",
                operator: "in",
                value: stationId
            });

The DataSource schema must be given a total value in order to page correctly. However, DataSource expects this value to come from a response body field. In some cases, we must work with systems that return the total value as a custom field in the response header. We need a way to read custom response header values. 

Yes, the DataSource transport uses jQuery.ajax, so we can implement a custom complete function to read the response headers from the jqXHR. However, complete fires AFTER schema.total is set so it does no good.

For easy using local arrays with kendo DataSource it would be good to have a functionallity to assign an array (kendo.obersvableHierarchy) without configure transport for CRUD operations.
When using Kendo MVVM it's easy then to define a grid the columns and field, and bind only the observable array as datasource.

And it would be great to have the possibility to assing depended arrays as field in an array that will be used as datasource for a grid or dropdown. Then we can assing the depended array of a selected dataitem to another control. So there is an need to have a special datatype like "dependedArray" and changes to this depended array has no effect to all ohter controls that where the viewmodel was bound.
Then we have more time to develope business logic. 

Although that the ListBox is similar to the MultiSelect, at the moment it does not have such model binding, because it is also comparable with the data management widgets and for the initial release of the ListBox our developers decided to consider the model binding only if there is demand for it. With that in mind, you could create a feature request in our public portal for that feature: 

http://www.telerik.com/forums/listbox-bind-to-model-view

I'm using Kendo UI with Vue wrappers. I have a grid that feeds from a remote datasource, but I have a custom implementation for the data service (using Axios). Currently, Kendo requires me to do this:
```
          <kendo-datasource ref="datasource" :data="rowData"></kendo-datasource>
          <kendo-grid :data-source-ref="'datasource'">
            <kendo-grid-column v-for="columnDef in columnDefs" :key="columnDef.field"
              :field="columnDef.field"
              :title="columnDef.headerName">
            </kendo-grid-column>
          </kendo-grid>
```

It seems like extra boiler plate to require the separate <kendo-datasource> tag. Why can't I bind my `rowData` directly to the kendo-grid?

One of key areas for enterprises is data security. If we can add the capability of encrypting data via kendo datasource, it would be awesome. 
This encryption should automatically happen when data is received from a service using the encryption algorithm specified as an attribute of kendo datasource. Similarly, decryption should also happen when the datasource receives the encrypted data.

See this forum post for details: http://www.kendoui.com/forums/framework/mvvm/getting-access-to-array-index-while-binding-an-array-source.aspx

see Ticket ID: 981260

var dataSource = new kendo.data.DataSource({
      type: "odata-v4",       
  });

works correct, but if you just define parameterMap
the payload of parameters is not "odata-v4" it changes to old odata
with this:

var dataSource = new kendo.data.DataSource({
        type: "odata-v4",
        transport: {
            parameterMap: function(data)
            {
                return data;
            }
        }
});

This feels like I set dataType JSON for transport, and if I just define beforeSend in Ajax Request,
I suddenly becomes XML just by defining a overwrite function.

Right aligned columns are common for number fields and it would be nice to simply set a property in HTML and/or the view-model:
E.g { "field": "amount", "align": "right", "title": "Amount", "width": "110" }

Please consider adding support for the new improved Signalr core to be used as an async data source and or server side rpc which would allow for greater mvvm spa applications 

Signalr is a push technology, but your current implementation is not robust enough to allow data from an outside source to be pushed to your grid. A stop measure for this would be to include the ability to use a function in addition to a string for the server read function. This would enable a developer to chain a server call to refresh data when data changes are coming from a source outside your grids. A full implementation of signalr would be to code your grid to accept a signalr call from the server hub that directly updates client data from any source, as long as it conforms to the model for the grid. This could be possibly done through the use of a signalr grid group, that the server could push to. This group should be a group of one that maps to a specific grid. This would also allow multiple grids on a page/form to be independently updated. Currently your signalr grids interfere with each other if the calls are running at the same time on that same page/form, both synchronously and asynchronously. 

"WebAPI now uses the DateTimeOffset time as a main type when it comes to dates. However DateTimeOffet requires the Model(that the dataSource creates) to keep information for both Date and Offset which is not possible with the current architecture of the DataSource and Model of Kendo." Based on http://docs.telerik.com/kendo-ui/aspnet-mvc/helpers/grid/how-to/oData-v4-web-api-controller
Please add full support, also when working with Dates. Thanks.

"Currently the custom offline storage does not support asynchronous requests". I received this response from Kendo support is response to an issue we have using SQLite for on offline storage. When we try this with local storage or session storage, dataSource.fetch().then() resolves correctly Please implement with SQLite.

When you have multiple spreadsheet components on the same HTML page, allow them to cross reference each other, similar to the existing referencing capability across multiple tabs (like worksheets) but across completely separate objects (like workbooks) - of course they would need to be on the same page.

Make spreadsheet support virtual scrolling as the grid does in this example - https://demos.telerik.com/kendo-ui/grid/virtualization-remote-data

This allows handling of much larger datasets than other methods of data binding.