I have grid with datasource of 15000 rows, where one page has 1000 rows. All filters always show checkboxes with all unique rows, even after i use filtration on grid and decrease row number. I want use excel-like filtering: when i use one filter in column on grid, then other column filters also refresh and show only unique values from current filtered grid.

I found example from telerik for this (.Examples.Mvc/Telerik.Examples.Mvc/Areas/GridFilterExcelLike), but it has a problem. It shows only unique values from grid.datasource.view(). It means it shows unique values in filter from one current page, and not uses other pages.

How can i can modify this example, so filters always show unique values from all grid?

Grid and DataSource:

@(Html.Kendo().DataSource<Telerik.Examples.Mvc.Areas.GridFilterExcelLike.Models.GridFilterExcelLikeProduct>()
    .Name("dataSourceShared")
    .Ajax(dataSource => dataSource
       .Read(read => read.Action("Products_Read", "Home"))
       .ServerOperation(false)
    )
)

@(Html.Kendo().Grid<Telerik.Examples.Mvc.Areas.GridFilterExcelLike.Models.GridFilterExcelLikeProduct>()
      .Name("grid")
      .DataSource(dataSource => dataSource
            .Ajax()
            .Read(read => read.Action("Products_Read", "Home"))
            .PageSize(20)
            .Events(events => events
             .Change("onChange")
      )
        )
      .Events(events => events
       .FilterMenuInit("onFilterMenuInit")
      )
      .Columns(columns =>
      {
          columns.Bound(product => product.ProductID).Filterable(ftb => ftb.Multi(true).DataSource("dataSourceShared"));
          columns.Bound(product => product.ProductName).Filterable(ftb => ftb.Multi(true).DataSource("dataSourceShared"));
          columns.Bound(product => product.UnitsInStock).Filterable(ftb => ftb.Multi(true).DataSource("dataSourceShared"));
          columns.Bound(product => product.UnitPrice).Filterable(ftb => ftb.Multi(true).DataSource("dataSourceShared"));
      })
      .Pageable()
      .Filterable()
      .Sortable()
)

Script from example:

<script>


    function onChange(e) {
        dataSourceShared.data(e.items);
    }

    function onFilterMenuInit(e) {
        var grid = e.sender;
        e.container.data("kendoPopup").bind("open", function () {
            dataSourceShared.sort({ field: e.field, dir: "asc" });
            var uniqueDsResult = removeDuplicates(grid.dataSource.view(), e.field);
            dataSourceShared.data(uniqueDsResult);
        })

        function removeDuplicates(items, field) {
            var getter = function (item) { return item[field] },
                result = [],
                index = 0,
                seen = {};

            while (index < items.length) {
                var item = items[index++],
                    text = getter(item);

                if (text !== undefined && text !== null && !seen.hasOwnProperty(text)) {
                    result.push(item);
                    seen[text] = true;
                }
            }

            return result;
        }
    }
</script>

And Datasource action

public ActionResult Products_Read([DataSourceRequest] DataSourceRequest request)
        {
            using (var northwind = new GridFilterExcelLikeEntities())
            {
                IQueryable<GridFilterExcelLikeProduct> products = northwind.Products;
                DataSourceResult result = products.ToDataSourceResult(request);
                return Json(result);
            }
        }