[DefaultValue(GridFilterPanelDisplayMode.Never)]
[Parameter]
public GridFilterPanelDisplayMode FilterPanelDisplayMode { get; set; }

@inject NwindDataService NwindDataService

<DxGrid @ref="Grid"
        Data="Data"
        FilterMenuButtonDisplayMode="GridFilterMenuButtonDisplayMode.Always"
        FilterPanelDisplayMode="GridFilterPanelDisplayMode.Always">
    <Columns>
        <DxGridDataColumn FieldName="SalesPerson" Caption="Salesperson" />
        <DxGridBandColumn Caption="Order">
            <Columns>
                <DxGridDataColumn FieldName="CompanyName" />
                <DxGridDataColumn FieldName="OrderDate" Caption="Date" />
                <DxGridBandColumn Caption="Product">
                    <Columns>
                        <DxGridDataColumn FieldName="ProductName" Caption="Name" />
                        <DxGridDataColumn FieldName="UnitPrice" DisplayFormat="c"
                                          CaptionAlignment="GridTextAlignment.Right" />
                    </Columns>
                </DxGridBandColumn>
                <DxGridDataColumn FieldName="Quantity" />
            </Columns>
        </DxGridBandColumn>
    </Columns>
</DxGrid>

@code {
    object Data { get; set; }
    IGrid Grid { get; set; }

    protected override async Task OnInitializedAsync() {
        var invoices = await NwindDataService.GetInvoicesAsync();
        var customers = await NwindDataService.GetCustomersAsync();
        Data = invoices.OrderBy(i => i.OrderDate).Join(customers, i => i.CustomerId, c => c.CustomerId,
            (i, c) => { return new {
                CompanyName = c.CompanyName,
                SalesPerson = i.Salesperson,
                UnitPrice = i.UnitPrice,
                OrderDate = i.OrderDate,
                ProductName = i.ProductName,
                Quantity = i.Quantity
            };
        });
    }
    protected override Task OnAfterRenderAsync(bool firstRender) {
        if (firstRender)
            Grid.SetFilterCriteria(CriteriaOperator.Parse("[UnitPrice] > 100M" +
                                                  "And ([SalesPerson] In ('Robert King', 'Andrew Fuller')" +
                                                  "Or [CompanyName] == 'Ernst Handel')"));
        return base.OnAfterRenderAsync(firstRender);
    }
}

using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;

namespace BlazorDemo.Data.Northwind {
    public class Invoice {
        public string ShipName { get; set; }
        public string ShipAddress { get; set; }
        public string ShipCity { get; set; }
        public string ShipRegion { get; set; }
        public string ShipPostalCode { get; set; }
        public string ShipCountry { get; set; }
        public string CustomerId { get; set; }
        public string CustomerName { get; set; }
        public string Address { get; set; }
        public string City { get; set; }
        public string Region { get; set; }
        public string PostalCode { get; set; }
        public string Country { get; set; }
        public string Salesperson { get; set; }
        public int OrderId { get; set; }
        public DateTime? OrderDate { get; set; }
        public DateTime? RequiredDate { get; set; }
        public DateTime? ShippedDate { get; set; }
        public string ShipperName { get; set; }
        public int ProductId { get; set; }
        public string ProductName { get; set; }
        public decimal UnitPrice { get; set; }
        public short Quantity { get; set; }
        public float Discount { get; set; }
        public decimal? ExtendedPrice { get; set; }
        public decimal? Freight { get; set; }
    }
}

using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;

namespace BlazorDemo.Data.Northwind {
    public partial class Customer {
        public Customer() {
            Orders = new HashSet<Order>();
        }

        public string CustomerId { get; set; }
        public string CompanyName { get; set; }
        public string ContactName { get; set; }
        public string ContactTitle { get; set; }
        public string Address { get; set; }
        public string City { get; set; }
        public string Region { get; set; }
        public string PostalCode { get; set; }
        public string Country { get; set; }
        public string Phone { get; set; }
        public string Fax { get; set; }

        public virtual ICollection<Order> Orders { get; set; }
    }
}

using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using BlazorDemo.Data.Northwind;
using BlazorDemo.DataProviders;

namespace BlazorDemo.Services {
    public partial class NwindDataService {
        public Task<IEnumerable<Invoice>> GetInvoicesAsync(CancellationToken ct = default) {
            // Return your data here
        }
        public Task<IEnumerable<Customer>> GetCustomersAsync(CancellationToken ct = default) {
            // Return your data here
        }
    }
}

// ...
builder.Services.AddScoped<NwindDataService>();