Index.razor

@page "/"
@rendermode InteractiveServer
@inject IJSRuntime JS
@using DevExpress.XtraReports.UI
@using GridMasterDetailExport.Data
@using GridMasterDetailExport.Reports

<DxGrid @ref="MasterGrid"
        AllowColumnReorder="false"
        AllowSort="false"
        Data="DataProvider.GetUsers()"
        KeyFieldName="UserID">
    <ToolbarTemplate Context="ctx">
        <DxToolbar>
            <Items>
                <DxToolbarItem Text="Export as PDF" Click="ExportToPdf" />
                <DxToolbarItem Text="Export as XLSX" Click="ExportToXlsx" />
                <DxToolbarItem Text="Export as CSV" Click="ExportToCsv" />
            </Items>
        </DxToolbar>
    </ToolbarTemplate>
    <Columns>
        <DxGridDataColumn FieldName="UserID" />
        <DxGridDataColumn FieldName="UserName" />
    </Columns>
    <DetailRowTemplate Context="ctx">
        @{
            User user = ctx.DataItem as User ?? new();
            var userOrders =
            DataProvider.GetOrders()
            .Where(o => o.UserID == user.UserID);
        }
        <DxGrid @ref="DetailGrid"
                AllowColumnReorder="false"
                AllowSort="false"
                Data="userOrders"
                KeyFieldName="OrderID">
            <Columns>
                <DxGridDataColumn FieldName="OrderID" />
                <DxGridDataColumn FieldName="OrderDate" />
                <DxGridDataColumn FieldName="ProductName" />
            </Columns>
        </DxGrid>
    </DetailRowTemplate>
</DxGrid>

@code {
    public DxGrid? MasterGrid { get; set; }

    public DxGrid? DetailGrid { get; set; }

    private async Task ExportToPdf() {
        using var report = GetReport();
        using var stream = new MemoryStream();
        await report.ExportToPdfAsync(stream);
        await DownloadStreamAsync(stream, "exportResult.pdf");
    }

    private async Task ExportToXlsx() {
        using var report = GetReport();
        using var stream = new MemoryStream();
        await report.ExportToXlsxAsync(stream);
        await DownloadStreamAsync(stream, "exportResult.xlsx");
    }

    private async Task ExportToCsv() {
        using var report = GetReport();
        using var stream = new MemoryStream();
        await report.ExportToCsvAsync(stream);
        await DownloadStreamAsync(stream, "exportResult.csv");
    }

    private XtraReport GetReport() {
        return ReportGenerationHelpers.GetReportFromDxGrid(
            GetVisibleColumnNames(MasterGrid),
            GetVisibleColumnNames(DetailGrid),
            GetRowsExpandedStates()
        );
    }

    private static string[] GetVisibleColumnNames(IGrid? grid) {
        return grid?.GetVisibleColumns()
                    .OfType<DxGridDataColumn>()
                    .Select(c => c.FieldName ?? c.Name).ToArray() ?? [];
    }

    private Dictionary<string, bool> GetRowsExpandedStates() {
        Dictionary<string, bool> masterRowExpandedStates = new();
        for(int i = 0; i < MasterGrid?.GetVisibleRowCount(); i++) {
            if(MasterGrid.GetDataItem(i) is User user) {
                masterRowExpandedStates[user.UserID.ToString()]
                    = MasterGrid.IsDetailRowExpanded(i);
            }
        }
        return masterRowExpandedStates;
    }

    async Task DownloadStreamAsync(Stream stream, string fileName) {

        stream.Seek(0, SeekOrigin.Begin);

        using var streamRef = new DotNetStreamReference(stream);
        await JS.InvokeVoidAsync("downloadFileFromStream", fileName, streamRef);
    }
}