//WPF
<Window x:Class="WpfApp4.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp4"
        mc:Ignorable="d"
        Title="{Binding MainTitle}" WindowState="Maximized">
    <Window.DataContext>
        <local:MainVM/>
    </Window.DataContext>
    <Window.Resources>
        <Style TargetType="TextBlock" x:Key="TbkStyle">
            <Setter Property="FontSize" Value="30"/>
            <Setter Property="FontWeight" Value="Normal"/>
            <Style.Triggers>
                <Trigger Property="IsMouseOver" Value="True">
                    <Setter Property="Foreground" Value="Red"/>
                    <Setter Property="FontWeight" Value="ExtraBold"/>
                </Trigger>
            </Style.Triggers>
        </Style>

        <ControlTemplate TargetType="ContentControl"
                         x:Key="DGControlTemplate">
            <DataGrid ItemsSource="{Binding BksCollection}"
                      AutoGenerateColumns="True"
                      CanUserAddRows="False"
                      VirtualizingPanel.IsVirtualizing="True"
                      VirtualizingPanel.VirtualizationMode="Recycling"
                      VirtualizingPanel.CacheLength="2,2"
                      VirtualizingPanel.CacheLengthUnit="Item"
                      ScrollViewer.CanContentScroll="True"
                      ScrollViewer.IsDeferredScrollingEnabled="True"
                      UseLayoutRounding="True"
                      SnapsToDevicePixels="True">
                <DataGrid.Resources>
                    <Style TargetType="DataGridRow">
                        <Setter Property="FontSize" Value="30"/>
                        <Setter Property="FontWeight" Value="Normal"/>
                        <Style.Triggers>
                            <Trigger Property="IsMouseOver" Value="True">
                                <Setter Property="Foreground" Value="Red"/>
                                <Setter Property="FontWeight" Value="ExtraBold"/>
                            </Trigger>
                        </Style.Triggers>
                    </Style>
                </DataGrid.Resources>
                <DataGrid.ContextMenu>
                    <ContextMenu>
                        <MenuItem Header="Load Data"
                                  Command="{Binding LoadCommand}"
                                  FontSize="30"
                                  Width="300"/>
                        <MenuItem Header="Export Selected"
                                  Command="{Binding ExportSelectedDataCommand}"
                                  CommandParameter="{Binding RelativeSource={RelativeSource AncestorType=ContextMenu},
                                  Path=PlacementTarget.SelectedItems}"
                                  Width="300"
                                  FontSize="30"/>
                    </ContextMenu>
                </DataGrid.ContextMenu>
            </DataGrid>
        </ControlTemplate>
    </Window.Resources>
    <Grid>
        <ContentControl Template="{StaticResource DGControlTemplate}"/>
    </Grid>
</Window>


using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Diagnostics;
using System.Diagnostics.Eventing.Reader;
using System.IO;
using System.Net.Http;
using System.Runtime.CompilerServices;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using Microsoft.Win32;
using Newtonsoft.Json;

namespace WpfApp4
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }
    }

    public class MainVM : INotifyPropertyChanged
    {
        private static HttpClient client = new HttpClient()
        {
            Timeout = TimeSpan.FromHours(1)
        };

        private static string originUrl = "http://localhost:59166/BookService.svc/getbooks?cnt=";
        private bool isLoading = false;
        private string tempMsg = "";
        public MainVM()
        {
            if (!DesignerProperties.GetIsInDesignMode(new DependencyObject()))
            {
                SetMainTitle(GetTimeNow());
                _ = InitBooksCollectionAsync();
            }
        }

        private async Task InitBooksCollectionAsync(int cnt = 1000000)
        {
            if (isLoading)
            {
                return;
            }
            isLoading = true;
            tempMsg = $"{GetTimeNow()},start loading...";
            SetMainTitle(tempMsg);
            try
            {
                string url = $"{originUrl}{cnt}";
                string jsonStr = await client.GetStringAsync(url);
                List<Book> bksList = JsonConvert.DeserializeObject<List<Book>>(jsonStr);
                if (bksList != null && bksList.Any())
                {
                    BksCollection = new ObservableCollection<Book>(bksList);
                    tempMsg = $"{GetTimeNow()},FirstId:{BksCollection?.FirstOrDefault()?.Id}," +
                        $"LastId:{BksCollection?.LastOrDefault()?.Id}";
                    SetMainTitle(tempMsg);
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex?.Message);
            }
            finally
            {
                isLoading = false;
            }
        }

        private ICommand loadCommand;
        public ICommand LoadCommand
        {
            get
            {
                if(loadCommand==null)
                {
                    loadCommand = new DelegateCommand(LoadCommandExecuted);
                }
                return loadCommand;
            }
        }

        private void LoadCommandExecuted(object obj)
        {
            _ = InitBooksCollectionAsync();
        }

        private ICommand exportSelectedDataCommand;
        public ICommand ExportSelectedDataCommand
        {
            get
            {
                if(exportSelectedDataCommand==null)
                {
                    exportSelectedDataCommand = new DelegateCommand(ExportSelectedDataCommandExecuted);
                }
                return exportSelectedDataCommand;
            }
        }

        private void ExportSelectedDataCommandExecuted(object obj)
        {
            var items = ((System.Collections.IList)obj).Cast<Book>()?.ToList();
            if(items!=null && items.Any())
            {
                string jsonStr = JsonConvert.SerializeObject(items, Formatting.Indented);
                SaveFileDialog dlg = new SaveFileDialog();
                dlg.Filter = "Json Files|*.json|All Files|*.*";
                dlg.FileName = $"Json_{GetTimeNow()}.json";
                if (dlg.ShowDialog() == true)
                {
                    using (StreamWriter jsonWriter = new StreamWriter(dlg.FileName, false, System.Text.Encoding.UTF8))
                    {
                        jsonWriter.WriteLine(jsonStr);
                        tempMsg = $"{GetTimeNow()},export {items.Count} items to {dlg.FileName}";
                        SetMainTitle(tempMsg);
                        MessageBox.Show(tempMsg);
                    }
                }
            }           
        }

        private void SetMainTitle(string msg)
        {
            Application.Current?.Dispatcher.Invoke(() =>
            {
                MainTitle = msg;
            }, System.Windows.Threading.DispatcherPriority.Background);
        }

        private ObservableCollection<Book> bksCollection;
        public ObservableCollection<Book> BksCollection
        {
            get
            {
                return bksCollection;
            }
            set
            {
                if (value != bksCollection)
                {
                    bksCollection = value;
                    OnPropertyChanged();
                }
            }
        }

        private string mainTitle;
        public string MainTitle
        {
            get
            {
                return mainTitle;
            }
            set
            {
                if (value != mainTitle)
                {
                    mainTitle = value;
                    OnPropertyChanged();
                }
            }
        }

        private string GetTimeNow()
        {
            return $"{DateTime.Now.ToString("yyyyMMddHHmmssffff")}";
        }

        public event PropertyChangedEventHandler? PropertyChanged;
        private void OnPropertyChanged([CallerMemberName] string propName = "")
        {
            var handler = Volatile.Read(ref PropertyChanged);
            if (handler == null)
            {
                return;
            }
            handler(this, new PropertyChangedEventArgs(propName));
        }
    }

    public class Book
    {
        public long Id { get; set; }
        public string Name { get; set; }
        public string CategoryName { get; set; }
        public string ISBN { get; set; }
        public string Comment { get; set; }
        public string Summary { get; set; }
        public string Title { get; set; }
        public string Topic { get; set; }
    }

    public class DelegateCommand : ICommand
    {
        private Action<object> execute;
        private Func<object?, bool>? canExecute;
        public DelegateCommand(Action<object> executeValue, Func<object?, bool>? canExecuteValue = null)
        {
            execute = executeValue;
            canExecute = canExecuteValue;
        }

        public event EventHandler? CanExecuteChanged;

        public bool CanExecute(object? parameter)
        {
            return canExecute == null ? true : canExecute(parameter);
        }

        public void Execute(object? parameter)
        {
            execute(parameter);
        }

        public void RaiseCanExecuted()
        {

        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.ServiceModel.Web;
using System.Text;

namespace WcfService2
{
    // NOTE: You can use the "Rename" command on the "Refactor" menu to change the interface name "IBookService" in both code and config file together.
    [ServiceContract]
    public interface IBookService
    {
        [OperationContract]
        [WebGet(UriTemplate = "/getbooks?cnt={cnt}",
            RequestFormat =WebMessageFormat.Json,
            ResponseFormat =WebMessageFormat.Json)]
        List<Book> GetBooks(int cnt = 100);
    }


    public class Book
    {
        public long Id { get; set; }
        public string Name { get; set; }
        public string CategoryName { get; set; }
        public string ISBN { get; set; }
        public string Comment { get; set; }
        public string Summary { get; set; }
        public string Title { get; set; }
        public string Topic { get; set; }
    }

    enum BookCategory
    {
        Science, Technology, Engineering, Math
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.Text;
using System.Threading;

namespace WcfService2
{
    // NOTE: You can use the "Rename" command on the "Refactor" menu to change the class name "BookService" in code, svc and config file together.
    // NOTE: In order to launch WCF Test Client for testing this service, please select BookService.svc or BookService.svc.cs at the Solution Explorer and start debugging.
    public class BookService : IBookService
    {
        private static string[] enumNames = Enum.GetNames(typeof(BookCategory));
        private static int enumsLen = enumNames.Length;
        private static Random rnd = new Random();
        private static long id = 1;
        private static (long, long) GetStartEnd(int cnt = 1000)
        {
            long end = Interlocked.Add(ref id, cnt);
            long start = end - cnt;
            return (start, end);
        }


        public List<Book> GetBooks(int cnt = 100)
        {
            List<Book> bksList = new List<Book>(cnt);
            var (start, end) = GetStartEnd(cnt);
            for (long i = start; i < end; i++)
            {
                bksList.Add(new Book()
                {
                    Id = i,
                    Name = $"Name_{i}",
                    CategoryName = $"{enumNames[rnd.Next(0, enumsLen)]}",
                    ISBN = $"ISBN_{i}_{Guid.NewGuid():N}",
                    Comment = $"Comment_{i}",
                    Summary = $"Summary_{i}",
                    Title = $"Title_{i}",
                    Topic = $"Topic_{i}"
                });
            }
            return bksList;
        }
    }
}


<?xml version="1.0"?>
<configuration>

    <appSettings>
        <add key="aspnet:UseTaskFriendlySynchronizationContext" value="true" />
    </appSettings>
    <system.web>
        <compilation debug="true" targetFramework="4.8" />
        <httpRuntime targetFramework="4.8"/>
    </system.web>
    <system.serviceModel>
        <bindings>
            <webHttpBinding>
                <binding name="BookServiceWebHttpBinding"
                         openTimeout="01:00:00"
                         closeTimeout="01:00:00"
                         sendTimeout="01:00:00"
                         receiveTimeout="01:00:00"
                         maxBufferPoolSize="2147483647"
                         maxBufferSize="2147483647"
                         maxReceivedMessageSize="2147483647">
                    <readerQuotas maxArrayLength="2147483647"
                                  maxBytesPerRead="2147483647"
                                  maxDepth="2147483647"
                                  maxNameTableCharCount="2147483647"
                                  maxStringContentLength="2147483647"/>
                    <security mode="None"/>
                </binding>
            </webHttpBinding>
        </bindings>
        <behaviors>
            <serviceBehaviors>
                <behavior name="BookServiceBehavior">
                    <!-- To avoid disclosing metadata information, set the values below to false before deployment -->
                    <serviceMetadata httpGetEnabled="true" httpsGetEnabled="true"/>
                    <!-- To receive exception details in faults for debugging purposes, set the value below to true.  Set to false before deployment to avoid disclosing exception information -->
                    <serviceDebug includeExceptionDetailInFaults="false"/>
                </behavior>
            </serviceBehaviors>
            <endpointBehaviors>
                <behavior name="BookServiceEndPointBehavior">
                    <webHttp/>
                </behavior>
            </endpointBehaviors>
        </behaviors>
        <protocolMapping>
            <add binding="basicHttpsBinding" scheme="https" />
        </protocolMapping>
        <serviceHostingEnvironment aspNetCompatibilityEnabled="true" multipleSiteBindingsEnabled="true" />
        <services>
            <service name="WcfService2.BookService"
                     behaviorConfiguration="BookServiceBehavior">
                <endpoint address=""
                          binding="webHttpBinding"
                          contract="WcfService2.IBookService"
                          behaviorConfiguration="BookServiceEndPointBehavior"
                          bindingConfiguration="BookServiceWebHttpBinding"/>
            </service>
        </services>
    </system.serviceModel>
    <system.webServer>
        <modules runAllManagedModulesForAllRequests="true"/>
        <!--
        To browse web app root directory during debugging, set the value below to true.
        Set to false before deployment to avoid disclosing web app folder information.
      -->
        <directoryBrowse enabled="true"/>
    </system.webServer>

</configuration>