DxGrid.WaitForInstantFeedbackRowLoadAsync(Int32) Method

Returns a task that is completed when the specified row of an asynchronous Instant Feedback Data Source is loaded.

Namespace: DevExpress.Blazor

Assembly: DevExpress.Blazor.v23.1.dll

NuGet Package: DevExpress.Blazor

Declaration

public Task WaitForInstantFeedbackRowLoadAsync(
    int visibleIndex
)

Parameters

Name	Type	Description
visibleIndex	Int32	The row’s visible index.

Returns

Type	Description
Task	The task that is completed when the row is loaded.

Remarks

An Instant Feedback Data Source is designed to work with large data collections. It loads data asynchronously in small portions on demand (instead of the entire dataset).

Call the WaitForInstantFeedbackRowLoadAsync method to ensure that the specified data row is loaded. For instance, call this method before those that accept a row’s visible index as a parameter (SelectRow, StartEditRowAsync, and so on).

For multiple rows, use the await Task.WhenAll(…) statement to combine multiple WaitForInstantFeedbackRowLoadAsync method calls.

The following example demonstrates how to select a row that is not yet loaded and is located outside the visible range:

Razor

@using Microsoft.EntityFrameworkCore
@using DevExpress.Data.Linq
@inject IDbContextFactory<NorthwindContext> NorthwindContextFactory
@implements IDisposable

<DxGrid Data="InstantFeedbackSource"
        AllowSelectRowByClick="true"
        KeyFieldName="OrderId"
        @ref="MyGrid"> 
    <Columns>
        <DxGridDataColumn FieldName="ShipName" />
        <DxGridDataColumn FieldName="ShipCity" />
        <DxGridDataColumn FieldName="ShipCountry" />
        <DxGridDataColumn FieldName="Freight"  />
        <DxGridDataColumn FieldName="OrderDate" />
        <DxGridDataColumn FieldName="ShippedDate" />
    </Columns>
</DxGrid>

<DxButton Click="OnSelectRow">Select Row 100</DxButton>

@code {
    EntityInstantFeedbackSource InstantFeedbackSource { get; set; }
    NorthwindContext Northwind { get; set; }
    IGrid MyGrid { get; set; }

    protected override void OnInitialized() {
        Northwind = NorthwindContextFactory.CreateDbContext();
        InstantFeedbackSource = new EntityInstantFeedbackSource(e => {
            e.KeyExpression = "OrderId";
            e.QueryableSource = Northwind.Orders;
        });
    }

    public async Task OnSelectRow() {
        await MyGrid.WaitForInstantFeedbackRowLoadAsync(100);
        MyGrid.SelectRow(100);
    }

    public void Dispose() {
        InstantFeedbackSource?.Dispose();
        Northwind?.Dispose();
    }
}

Order

using System;
using System.Collections.Generic;

#nullable disable

namespace Grid.Northwind {
    public partial class Order {
        public Order() {
            OrderDetails = new HashSet<OrderDetail>();
        }

        public int OrderId { get; set; }
        public string CustomerId { get; set; }
        public int? EmployeeId { get; set; }
        public DateTime? OrderDate { get; set; }
        public DateTime? RequiredDate { get; set; }
        public DateTime? ShippedDate { get; set; }
        public int? ShipVia { get; set; }
        public decimal? Freight { get; set; }
        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 virtual Customer Customer { get; set; }
        public virtual Shipper ShipViaNavigation { get; set; }
        public virtual ICollection<OrderDetail> OrderDetails { get; set; }
    }
}

NorthwindContext

using Microsoft.EntityFrameworkCore;
#nullable disable

namespace Grid.Northwind {
    public partial class NorthwindContext : DbContext {

        public NorthwindContext(DbContextOptions<NorthwindContext> options)
            : base(options) {
        }
        // ...
        public virtual DbSet<Order> Orders { get; set; }
        // ...

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) {
            if(!optionsBuilder.IsConfigured) {
                optionsBuilder.UseSqlServer("Server=.\\sqlexpress;Database=Northwind;Integrated Security=true");
            }
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder) {
            modelBuilder.HasAnnotation("Relational:Collation", "SQL_Latin1_General_CP1_CI_AS");
            // ...
            modelBuilder.Entity<Order>(entity => {
                entity.HasIndex(e => e.CustomerId, "CustomerID");
                entity.HasIndex(e => e.CustomerId, "CustomersOrders");
                entity.HasIndex(e => e.EmployeeId, "EmployeeID");
                entity.HasIndex(e => e.EmployeeId, "EmployeesOrders");
                entity.HasIndex(e => e.OrderDate, "OrderDate");
                entity.HasIndex(e => e.ShipPostalCode, "ShipPostalCode");
                entity.HasIndex(e => e.ShippedDate, "ShippedDate");
                entity.HasIndex(e => e.ShipVia, "ShippersOrders");
                entity.Property(e => e.OrderId).HasColumnName("OrderID");
                entity.Property(e => e.CustomerId)
                    .HasMaxLength(5)
                    .HasColumnName("CustomerID")
                    .IsFixedLength(true);
                entity.Property(e => e.EmployeeId).HasColumnName("EmployeeID");
                entity.Property(e => e.Freight)
                    .HasColumnType("money")
                    .HasDefaultValueSql("((0))");
                entity.Property(e => e.OrderDate).HasColumnType("datetime");
                entity.Property(e => e.RequiredDate).HasColumnType("datetime");
                entity.Property(e => e.ShipAddress).HasMaxLength(60);
                entity.Property(e => e.ShipCity).HasMaxLength(15);
                entity.Property(e => e.ShipCountry).HasMaxLength(15);
                entity.Property(e => e.ShipName).HasMaxLength(40);
                entity.Property(e => e.ShipPostalCode).HasMaxLength(10);
                entity.Property(e => e.ShipRegion).HasMaxLength(15);
                entity.Property(e => e.ShippedDate).HasColumnType("datetime");
                entity.HasOne(d => d.Customer)
                    .WithMany(p => p.Orders)
                    .HasForeignKey(d => d.CustomerId)
                    .HasConstraintName("FK_Orders_Customers");
                entity.HasOne(d => d.ShipViaNavigation)
                    .WithMany(p => p.Orders)
                    .HasForeignKey(d => d.ShipVia)
                    .HasConstraintName("FK_Orders_Shippers");
            });
            // ...
            OnModelCreatingPartial(modelBuilder);
        }

        partial void OnModelCreatingPartial(ModelBuilder modelBuilder);
    }
}

Program.cs

using Microsoft.EntityFrameworkCore;
// ...
builder.Services.AddDbContextFactory<NorthwindContext>((sp, options) => {
    var env = sp.GetRequiredService<IWebHostEnvironment>();
    var dbPath = Path.Combine(env.ContentRootPath, "Northwind-5e44b51f.mdf");
    options.UseSqlServer("Server=(localdb)\\MSSQLLocalDB;Integrated Security=true;AttachDbFileName=" + dbPath);
});

Implements

WaitForInstantFeedbackRowLoadAsync(Int32)