[ContentProperty("Target")]    public class GridLineDecorator : FrameworkElement    {        private ListView _target;        private DrawingVisual _gridLinesVisual = new DrawingVisual();        private GridViewHeaderRowPresenter _headerRowPresenter = null;        public GridLineDecorator()        {            this.AddVisualChild(_gridLinesVisual);            this.AddHandler(ScrollViewer.ScrollChangedEvent, new RoutedEventHandler(OnScrollChanged));        }        #region GridLineBrush        /// 
          /// GridLineBrush Dependency Property          /// 
          public static readonly DependencyProperty GridLineBrushProperty =            DependencyProperty.Register("GridLineBrush", typeof(Brush), typeof(GridLineDecorator),                new FrameworkPropertyMetadata(Brushes.LightGray,                    new PropertyChangedCallback(OnGridLineBrushChanged)));        /// 
          /// Gets or sets the GridLineBrush property.  This dependency property           /// indicates ....          /// 
          public Brush GridLineBrush        {            get { return (Brush)GetValue(GridLineBrushProperty); }            set { SetValue(GridLineBrushProperty, value); }        }        /// 
          /// Handles changes to the GridLineBrush property.          /// 
          private static void OnGridLineBrushChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)        {            ((GridLineDecorator)d).OnGridLineBrushChanged(e);        }        /// 
          /// Provides derived classes an opportunity to handle changes to the GridLineBrush property.          /// 
          protected virtual void OnGridLineBrushChanged(DependencyPropertyChangedEventArgs e)        {            DrawGridLines();        }        #endregion        #region Target        public ListView Target        {            get { return _target; }            set            {                if (_target != value)                {                    if (_target != null) Detach();                    RemoveVisualChild(_target);                    RemoveLogicalChild(_target);                    _target = value;                    AddVisualChild(_target);                    AddLogicalChild(_target);                                     if (_target != null) Attach();                    InvalidateMeasure();                }            }        }        private void GetGridViewHeaderPresenter()        {            if (Target == null)            {                _headerRowPresenter = null;                return;            }            _headerRowPresenter = Target.GetDesendentChild
     
      ();        }        #endregion        #region DrawGridLines        private void DrawGridLines()        {            if (Target == null) return;            if (_headerRowPresenter == null) return;            var itemCount = Target.Items.Count;            if (itemCount == 0) return;            var gridView = Target.View as GridView;            if (gridView == null) return;                   // 获取drawingContext              var drawingContext = _gridLinesVisual.RenderOpen();            var startPoint = new Point(0, 0);            // 为了对齐到像素的计算参数，否则就会看到有些线是模糊的              var dpiFactor = this.GetDpiFactor();            var pen = new Pen(this.GridLineBrush, 1 * dpiFactor);            var halfPenWidth = pen.Thickness / 2;            var guidelines = new GuidelineSet();            // 计算表头的偏移量和大小              var headerOffset = _headerRowPresenter.TranslatePoint(startPoint, this);            var headerSize = _headerRowPresenter.RenderSize;            var headerBottomY = headerOffset.Y + headerSize.Height;            // 计算ScrollViewer的可视区域大小              var item0 = _target.ItemContainerGenerator.ContainerFromIndex(0);            if (item0 == null) return;            var scrollViewer = item0.GetAncestor
      
       ();            if (scrollViewer == null) return;            var contentElement = scrollViewer.Content as UIElement;            var maxLineX = scrollViewer.ViewportWidth;            var maxLineY = headerBottomY + contentElement.RenderSize.Height;            var vLineY = 0.0;            // 画横线              for (int i = 0; i < itemCount; i++)            {                var item = Target.ItemContainerGenerator.ContainerFromIndex(i) as ListViewItem;                if (item != null)                {                    var renderSize = item.RenderSize;                    var offset = item.TranslatePoint(startPoint, this);                    var hLineX1 = offset.X;                    var hLineX2 = offset.X + renderSize.Width;                    var hLineY = offset.Y + renderSize.Height;                    vLineY = hLineY;                    // 小于视图起始位置的不绘制                      if (hLineY <= headerBottomY) continue;                    // 大于视图结束位置之后的不绘制                      if (hLineY > maxLineY) break;                    // 如果大于横向宽度，取横向宽度                      if (hLineX2 > maxLineX) hLineX2 = maxLineX;                    // 加入参考线，对齐到像素                      guidelines.GuidelinesY.Add(hLineY + halfPenWidth);                    drawingContext.PushGuidelineSet(guidelines);                    drawingContext.DrawLine(pen, new Point(hLineX1, hLineY), new Point(hLineX2, hLineY));                    drawingContext.Pop();                }            }                         //画竖线              var columns = gridView.Columns;            var vLineX = headerOffset.X;            if (vLineY > maxLineY) vLineY = maxLineY;            foreach (var column in columns)            {                var columnWidth = column.GetColumnWidth();                vLineX += columnWidth;                if (vLineX > maxLineX) break;                //加入参考线，对齐到像素                  guidelines.GuidelinesX.Add(vLineX + halfPenWidth);                drawingContext.PushGuidelineSet(guidelines);                drawingContext.DrawLine(pen, new Point(vLineX, headerBottomY), new Point(vLineX, vLineY));                drawingContext.Pop();            }                       drawingContext.Close();        }        #endregion        #region Overrides to show Target and grid lines        protected override int VisualChildrenCount        {            get { return Target == null ? 1 : 2; }        }        protected override System.Collections.IEnumerator LogicalChildren        {            get { yield return Target; }        }        protected override Visual GetVisualChild(int index)        {            if (index == 0) return _target;            if (index == 1) return _gridLinesVisual;            throw new IndexOutOfRangeException(string.Format("Index of visual child '{0}' is out of range", index));        }        protected override Size MeasureOverride(Size availableSize)        {            if (Target != null)            {                Target.Measure(availableSize);                return Target.DesiredSize;            }            return base.MeasureOverride(availableSize);        }        protected override Size ArrangeOverride(Size finalSize)        {            if (Target != null)                Target.Arrange(new Rect(new Point(0, 0), finalSize));            return base.ArrangeOverride(finalSize);        }        #endregion        #region Handle Events        private void Attach()        {            _target.Loaded += OnTargetLoaded;            _target.Unloaded += OnTargetUnloaded;            _target.SizeChanged += OnTargetSizeChanged;            _target.DragEnter += _target_DragEnter;        }        void _target_DragEnter(object sender, DragEventArgs e)        {            DrawGridLines();        }        private void Detach()        {            _target.Loaded -= OnTargetLoaded;            _target.Unloaded -= OnTargetUnloaded;            _target.SizeChanged -= OnTargetSizeChanged;        }        private void OnTargetLoaded(object sender, RoutedEventArgs e)        {            if (_headerRowPresenter == null)                GetGridViewHeaderPresenter();            DrawGridLines();        }        private void OnTargetUnloaded(object sender, RoutedEventArgs e)        {            DrawGridLines();        }        private void OnTargetSizeChanged(object sender, SizeChangedEventArgs e)        {            DrawGridLines();        }        private void OnScrollChanged(object sender, RoutedEventArgs e)        {            DrawGridLines();        }        #endregion      }
      
     

　　GridViewColumnHelper

internal  static class GridViewColumnHelper    {        private static PropertyInfo DesiredWidthProperty =           typeof(GridViewColumn).GetProperty("DesiredWidth", BindingFlags.NonPublic | BindingFlags.Instance);        public static double GetColumnWidth(this GridViewColumn column)        {            return (double.IsNaN(column.Width)) ? (double)DesiredWidthProperty.GetValue(column, null) : column.Width;        }      }

　　

VisualService

public static class VisualService    {        public static double GetDpiFactor(this Visual target)        {            var source = PresentationSource.FromVisual(target);            return source == null ? 1.0 : 1 / source.CompositionTarget.TransformToDevice.M11;        }        public static T GetAncestor
     
      (this DependencyObject target)            where T : DependencyObject        {            var parent = VisualTreeHelper.GetParent(target);            if (parent is T)                return (T)parent;            if (parent != null)                return parent.GetAncestor
      
       ();            return null;        }        public static T GetDesendentChild
       
        (this DependencyObject target)            where T : DependencyObject        {            var childCount = VisualTreeHelper.GetChildrenCount(target);            if (childCount == 0) return null;            for (int i = 0; i < childCount; i++)            {                var current = VisualTreeHelper.GetChild(target, i);                if (current is T)                    return (T)current;                var desendent = current.GetDesendentChild
        
         ();                if (desendent != null)                    return desendent;            }            return null;        }    }
        
       
      
     

 

 

                 
      
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