<telerik:RadGridView
    ItemsSource="{Binding Products}"
    SelectedItem="{Binding SelectedProduct, Mode=TwoWay}">
    ...
</telerik:RadGridView>

DragDropManager.AddDragInitializeHandler(icImages, OnDragInitialize);

private void OnDragInitialize(object sender, DragInitializeEventArgs e)
        {
          
            clsImage imageData = (clsImage)((FrameworkElement)e.OriginalSource).DataContext;

            DragDropData dragData = new DragDropData
            {
                ImageData = imageData ,
                Column = Column
            };

            e.Data = dragData;
            e.DragVisual = new ContentControl { ContentTemplate = LayoutRoot.Resources["ImageTemplate"] as DataTemplate, Content = imageData };
            e.AllowedEffects = DragDropEffects.All;

            e.Handled = true;
        }

            <DataTemplate x:Key="ImageTemplate">
                <Grid>
                    <telerik:RadSvgImage
                        UriSource="{Binding file}"
                        HorizontalAlignment="Left"
                        SizeType="ContentToSizeStretch"
                        OverrideColor="{Binding ImageColor}"
                        />
                </Grid>
            </DataTemplate>

<Window x:Class="TestVirtGrid.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:TestVirtGrid"
        xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation" 
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="*"/>
            <RowDefinition Height="50"/>
        </Grid.RowDefinitions>
        <telerik:RadVirtualGrid x:Name="VirtGrid" CanUserEdit="False" Grid.Row="0" SelectionMode="Multiple" SelectionUnit="Row" />
        <Button Grid.Row ="1" Content="amon"/>
    </Grid>
</Window>

using System.Collections.ObjectModel;
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 Telerik.Windows.Controls.VirtualGrid;

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

            ObservableCollection<Test> list = [];
            for (int i = 0; i < 20; i++)
                list.Add(new Test() { a = i, b = i });
            VirtGrid.DataProvider = new DataProvider(list);
        }

    }
    public class Test
    {
        public int a { get; set; }
        public int b { get; set; }
    }
}

    public class clsCloudUploadProvider : ICloudUploadProvider
    {
		long uploadFilesCount = 0;

		clsReklamation Reklamation;

		public Task<object> UploadFileAsync(string fileName, Stream fileStream, CloudUploadFileProgressChanged uploadProgressChanged, CancellationToken cancellationToken)
		{
			return Task.Factory.StartNew<object>(() => UploadFile(fileName, fileStream, uploadProgressChanged, cancellationToken), cancellationToken);
		}

		private object UploadFile(string fileName, Stream fileStream, CloudUploadFileProgressChanged uploadProgressChanged, CancellationToken cancellationToken)
		{
			this.uploadFilesCount++;
			var fileLength = fileStream.Length;

			uploadProgressChanged(fileLength);

			object[] ImportState = Import(fileStream, fileName);

			if ((bool)ImportState[0])
			{
				return fileName;
			}
			else
			{
				return null;
            }
		}

		public object[] Import(Stream filestream, string filename)
		{
			return clsDaten.UploadReklamationsDateienKEMdoc(Reklamation, (filestream as FileStream).Name);
		}

		public clsCloudUploadProvider(clsReklamation reklamation)
		{
			Reklamation = reklamation;
		}
	}