InfiniteScrollViewer lazy Data Loading Scrolling

InfiniteScrollViewer.cs

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Markup;

[assembly: XmlnsDefinition("http://codingsack.com/wpf/InfiniteScrollViewer", "InfiniteScrollViewerControl")]
[assembly: XmlnsPrefix("http://codingsack.com/wpf/InfiniteScrollViewer", "cs")]
namespace InfiniteScrollViewerControl
{
    public class InfiniteScrollViewer : ScrollViewer
    {
        static InfiniteScrollViewer()
        {
            DefaultStyleKeyProperty.OverrideMetadata(typeof(InfiniteScrollViewer), new FrameworkPropertyMetadata(typeof(InfiniteScrollViewer)));
        }
        public static DependencyProperty CommandProperty = DependencyProperty.Register("Command", typeof(ICommand), typeof(InfiniteScrollViewer));
        public static DependencyProperty CommandParameterProperty = DependencyProperty.Register("CommandParameter", typeof(object), typeof(InfiniteScrollViewer));
        public static DependencyProperty ScrollResetProperty = DependencyProperty.Register("ScrollReset", typeof(bool), typeof(InfiniteScrollViewer), new PropertyMetadata(new PropertyChangedCallback(OnScrollResetPropertyChanged)));
        public static DependencyProperty IsLoadingProperty = DependencyProperty.Register("IsLoading", typeof(bool), typeof(InfiniteScrollViewer), new PropertyMetadata(new PropertyChangedCallback(OnScrollIsLoadingPropertyChanged)));
        public static DependencyProperty LoadingContentProperty = DependencyProperty.Register("LoadingContent", typeof(object), typeof(InfiniteScrollViewer), new PropertyMetadata());

        private static void OnScrollResetPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
            var scrollviewer = sender as InfiniteScrollViewer;
            //if user want to set the scroll at top.
            //then he must changed  ScrollReset =true
            scrollviewer.ScrollToVerticalOffset(0);
        }
        private static void OnScrollIsLoadingPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
            var scrollviewer = sender as InfiniteScrollViewer;
            if (scrollviewer.IsLoading == false)
            {
                var ui = scrollviewer.LoadingContent as FrameworkElement;
                if (ui != null)
                {
                    //when IsLading is False then Hide the LoadingContent as well as Move Scroll to Up
                    scrollviewer.ScrollToVerticalOffset(scrollviewer.VerticalOffset - ui.DesiredSize.Height - ui.DesiredSize.Height);
                }
            }
           
        }
        public ICommand Command
        {
            get
            {
                return (ICommand)GetValue(CommandProperty);
            }
            set
            {
                SetValue(CommandProperty, value);
            }
        }
        public object CommandParameter
        {
            get
            {
                return GetValue(CommandParameterProperty);
            }

            set
            {
                SetValue(CommandParameterProperty, value);
            }
        }

        public bool ScrollReset
        {
            get
            {
                return (bool)GetValue(ScrollResetProperty);
            }
            set
            {
                SetValue(ScrollResetProperty, value);
            }
        }
        public bool IsLoading
        {
            get
            {
                return (bool)GetValue(IsLoadingProperty);
            }
            set
            {
                SetValue(IsLoadingProperty, value);
            }
        }
        public Object LoadingContent
        {
            get
            {
                return GetValue(LoadingContentProperty);
            }
            set
            {
                SetValue(LoadingContentProperty, value);
            }
        }
        
        protected override void OnScrollChanged(ScrollChangedEventArgs e)
        {
            base.OnScrollChanged(e);
            if (VerticalOffset > 0)
            {
                //As User has moved Scroll Down So Scroll Is not More at its Reset Position Which is TOP
                if (ScrollReset)
                {
                    ScrollReset = false;
                }
                //Scroll movied to the end of the Page
                if (VerticalOffset == ScrollableHeight)
                {
                    if (Command != null)
                    {
                        //See if we can Exeute the Command
                        if (Command.CanExecute(CommandParameter))
                        {
                            try
                            {
                                //execute the Command
                                Command.Execute(CommandParameter);
                            }
                            catch (Exception)
                            {
                                Command.Execute(null);
                            }
                        }
                    }
                }
            }
        }
    }
}

Style.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    
                     xmlns:po="http://schemas.microsoft.com/winfx/2006/xaml/presentation/options"
                   xmlns:local="clr-namespace:InfiniteScrollViewerControl"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
                    
             mc:Ignorable="d"
    >
    <Border x:Key="loader" Margin="10"   BorderThickness="3">
        <StackPanel>
            <TextBlock HorizontalAlignment="Center">Please Wait..</TextBlock>
            <ProgressBar Height="10" IsIndeterminate="True" Orientation="Horizontal" />
        </StackPanel>
    </Border>
    <Style  TargetType="{x:Type local:InfiniteScrollViewer}">
        <Setter Property="LoadingContent" Value="{StaticResource loader}"/>
        <Setter Property="IsLoading" Value="False"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type local:InfiniteScrollViewer}">
                    <Grid>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="*" />
                            <ColumnDefinition Width="Auto" />
                        </Grid.ColumnDefinitions>
                        <Grid.RowDefinitions>
                            <RowDefinition Height="*"/>
                            <RowDefinition Height="Auto"/>
                        </Grid.RowDefinitions>
                        <Grid  >
                            <Grid.RowDefinitions>
                                <RowDefinition Height="*"/>
                                <RowDefinition Height="Auto"/>
                            </Grid.RowDefinitions>
                            <ScrollContentPresenter />
                            <DockPanel Grid.Row="1" x:Name="loader" >
                                <ContentControl  Content="{TemplateBinding LoadingContent}" />
                            </DockPanel>
                        </Grid>
                        <ScrollBar
                Name="PART_VerticalScrollBar"
                Opacity="0.75"
                Grid.Column="1"
                Value="{TemplateBinding VerticalOffset}"
                Maximum="{TemplateBinding ScrollableHeight}"
                ViewportSize="{TemplateBinding ViewportHeight}"
                Visibility="{TemplateBinding ComputedVerticalScrollBarVisibility}" />
                        <ScrollBar
                Name="PART_HorizontalScrollBar"
                Orientation="Horizontal"
                Opacity="0.75"
                Grid.Row="1"
                Value="{TemplateBinding HorizontalOffset}"
                Maximum="{TemplateBinding ScrollableWidth}"
                ViewportSize="{TemplateBinding ViewportWidth}"
                Visibility="{TemplateBinding ComputedHorizontalScrollBarVisibility}" />
                    </Grid>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsLoading" Value="False">
                            <Setter TargetName="loader" Property="Visibility" Value="Collapsed"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>