TouchScroller.cs

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

namespace XeRetail.FrontOffice.UI.CustomControls
{
    public class TouchScroller : ScrollViewer
    {
        private double _firstMousePosition;
        private bool _isScrolling;
        private double _scrollingPace;

        public TouchScroller()
        {
            _scrollingPace = 0.1;
            var middleMousePosition = double.NaN;

            PreviewMouseLeftButtonDown += (s, e) => { _firstMousePosition = e.GetPosition(this).Y; };

            MouseLeftButtonUp += (s, e) =>
            {
                middleMousePosition = double.NaN;

                IsScrolling = false;
            };

            PreviewMouseMove += (s, e) =>
            {
                if (e.LeftButton == MouseButtonState.Pressed)
                {
                    var lastMousePosition = e.GetPosition(this).Y;

                    if (double.IsNaN(middleMousePosition)) middleMousePosition = _firstMousePosition;

                    ScrollToVerticalOffset(VerticalOffset - (lastMousePosition - middleMousePosition) * _scrollingPace);

                    middleMousePosition = lastMousePosition;

                    if (IsScrolling == false)
                        if (Math.Abs(lastMousePosition - _firstMousePosition) > 10)
                            IsScrolling = true;
                }
            };

            AddHandler(MouseLeftButtonUpEvent,
                new MouseButtonEventHandler((o, arg) =>
                {
                    middleMousePosition = double.NaN;

                    IsScrolling = false;
                }),
                true);
        }

        public bool IsScrolling
        {
            get => _isScrolling;

            set
            {
                if (_isScrolling == value)
                    return;

                _isScrolling = value;

                RaiseIsScrollingChanged?.Invoke(this, value);
            }
        }

        public void SetScrollingPace(double pace)
        {
            _scrollingPace = pace;
        }

        public event EventHandler<bool> RaiseIsScrollingChanged;
    }
}