Async ItemsProvider & Database Query Pushdown

Remote Provider

When managing enterprise datasets with hundreds of thousands of records, loading all rows into in-memory Blazor collections is inefficient. The ItemsProvider architecture provides an asynchronous, on-demand callback delegate (GridItemsProvider<T>) that requests only the slice of records required by the viewport.

Filter expressions, search phrases, sort orders, and pagination offsets are passed directly into the provider request, enabling 100% database query pushdown with zero memory consumption on the Blazor server.

Live Demo

Remote Search: Total Matches in DB: 0 | Active Window: 0 rows retrieved

Item Code	Item Description	Phase Code	Phase Description	Cost Category	UOM	Unit Price


No records to display

0 rows

@using Fx.ControlKit
@using Fx.ControlKit.Grid

<!-- ItemsProvider delegates viewport slices directly to backend queries -->
<GridControl TValue="EstimatingItemRecord"
             ItemsProvider="@_itemsProvider"
             Height="380px"
             AllowSorting="true"
             AllowSelection="true">
    <GridColumnsBase>
        <GridColumn Field="@nameof(EstimatingItemRecord.Item)" HeaderText="Item Code" Width="110px" />
        <GridColumn Field="@nameof(EstimatingItemRecord.ItemDesc)" HeaderText="Item Description" Width="260px" />
        <GridColumn Field="@nameof(EstimatingItemRecord.Phase)" HeaderText="Phase" Width="100px" />
        <GridColumn Field="@nameof(EstimatingItemRecord.Price)" HeaderText="Unit Price" Width="110px" Format="$#,##0.00" />
    </GridColumnsBase>
</GridControl>

@code {
    private GridItemsProvider<EstimatingItemRecord> _itemsProvider;

    protected override void OnInitialized()
    {
        _itemsProvider = async request =>
        {
            // Query SQLite or EF Core DB asynchronously
            var (rows, total) = await DbService.FetchSliceAsync(request.StartIndex, request.Count, request.CancellationToken);
            return GridItemsProviderResult.From(rows, total);
        };
    }
}

Feature Overview & Architecture Notes

ItemsProvider Implementation Guide

On-Demand Delegated Requests: The grid invokes the delegate passing a GridItemsProviderRequest<T> object with StartIndex, Count, and Sort parameters.
Pushdown SQL Execution: In a real database environment (e.g. SQLite, SQL Server, PostgreSQL), translate request.StartIndex into SQL OFFSET and Count into FETCH NEXT.
Total Count Contract: The provider returns a GridItemsProviderResult<T> containing the page of items and the TotalItemCount, allowing the grid scrollbar to reflect true dataset dimensions.

Request Parameters Contract

Member	Type	Description
`StartIndex`	int	Zero-based offset of the first record requested by the viewport.
`Count`	int	Number of records required to satisfy the scroll window plus overscan.
`CancellationToken`	CancellationToken	Enables early abort if the operator scrolls past quickly before results return.