可擦除完成，需要实现画笔，是不是还得用ink来做比较好

AIStudio.Wpf.DiagramDesigner/ViewModels/BaseViewModel/SelectableViewModelBase.cs

@@ -185,6 +185,11 @@ namespace AIStudio.Wpf.DiagramDesigner
             get; set;
         }
 
+        public bool DisableSelected
+        {
+            get;set;
+        } 
+
         private bool _isSelected;
         [Browsable(false)]
         //[CanDo]
@@ -192,6 +197,10 @@ namespace AIStudio.Wpf.DiagramDesigner
         {
             get
             {
+                if (DisableSelected == true)
+                {
+                    return false;
+                }
                 return _isSelected;
             }
             set

AIStudio.Wpf.DiagramDesigner/ViewModels/DrawingViewModel/Erasable/DrawingDesignerItemViewModelBase.cs

@@ -34,6 +34,7 @@ namespace AIStudio.Wpf.DiagramDesigner
             DrawMode = drawMode;
             Points = points;
             Erasable = erasable;
+            DisableSelected = Erasable;
         }
 
         public virtual bool OnMouseMove(IInputElement sender, MouseEventArgs e)
@@ -66,7 +67,7 @@ namespace AIStudio.Wpf.DiagramDesigner
 
         public virtual bool Erase(Geometry erase)
         {
-            if (Erasable)
+            if (Erasable && Keyboard.IsKeyDown(Key.LeftShift) == false)
             {
                 erase.Transform = new TranslateTransform(0 - Left, 0 - Top);
                 Geometry = Geometry.Combine(Geometry, erase, GeometryCombineMode.Exclude, null);
@@ -135,7 +136,6 @@ namespace AIStudio.Wpf.DiagramDesigner
         protected override void Init(IDiagramViewModel root, bool initNew)
         {
             base.Init(root, initNew);
-            IsHitTestVisible = false;
         }
 
         protected override void InitNew()

AIStudio.Wpf.DiagramDesigner/ViewModels/DrawingViewModel/Erasable/EraserDrawingDesignerItemViewModel.cs

@@ -4,6 +4,7 @@ using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 using System.Windows;
+using System.Windows.Documents;
 using System.Windows.Input;
 using System.Windows.Media;
 using SvgPathProperties;
@@ -30,38 +31,7 @@ namespace AIStudio.Wpf.DiagramDesigner
 
         public override bool OnMouseMove(IInputElement sender, MouseEventArgs e)
         {
-            if (e.RightButton == MouseButtonState.Pressed)
+            if (e.LeftButton == MouseButtonState.Pressed)
-            {
-                var point = e.GetPosition(sender);
-                if (Points == null || Points.Count == 0)//没有起始点
-                {
-                    return true;
-                }
-
-                if ((Points.LastOrDefault() - point).Length < ColorViewModel.LineWidth)
-                {
-                    return true;
-                }
-
-                Points.Add(point);
-                if (Geometry is PathGeometry geometry)
-                {
-
-                }
-                else
-                {
-                    geometry = new PathGeometry();
-                    var figure = new PathFigure { StartPoint = Points[0] };
-                    geometry.Figures.Add(figure);
-                }
-
-                LineSegment arc = new LineSegment(point, true);// { IsSmoothJoin = true };
-                geometry.Figures[0].Segments.Add(arc);
-                Geometry = geometry;
-
-                return true;
-            }
-            else if (e.LeftButton == MouseButtonState.Pressed)
             {
                 var point = e.GetPosition(sender);
                 if (Points == null || Points.Count == 0)//没有起始点
@@ -75,11 +45,30 @@ namespace AIStudio.Wpf.DiagramDesigner
                 }
 
                 var geometry = new PathGeometry();
-                var figure = new PathFigure { StartPoint = Points[0] };
+                var figure = new PathFigure { IsClosed = true, IsFilled = true };
                 geometry.Figures.Add(figure);
 
-                LineSegment arc = new LineSegment(point, true);// { IsSmoothJoin = true };
+                var radius = ColorViewModel.LineWidth / 2;
-                geometry.Figures[0].Segments.Add(arc);
+                var positiveX = radius * (point.X > Points[0].X ? 1 : -1);
+                var positiveY = radius * (point.Y > Points[0].Y ? 1 : -1);
+
+                figure.StartPoint = new Point(Points[0].X - positiveX, Points[0].Y - positiveY);
+
+                var line = new LineSegment(new Point(Points[0].X + positiveX, Points[0].Y - positiveY), false);
+                figure.Segments.Add(line);
+
+                line = new LineSegment(new Point(point.X + positiveX, point.Y - positiveY), false);
+                figure.Segments.Add(line);
+
+                line = new LineSegment(new Point(point.X + positiveX, point.Y + positiveY), false);
+                figure.Segments.Add(line);
+
+                line = new LineSegment(new Point(point.X - positiveX, point.Y + positiveY), false);
+                figure.Segments.Add(line);
+
+                line = new LineSegment(new Point(Points[0].X - positiveX, Points[0].Y + positiveY), false);
+                figure.Segments.Add(line);
+
                 Geometry = geometry;
                 Points[0] = point;
                 Erase(Geometry);
@@ -100,10 +89,6 @@ namespace AIStudio.Wpf.DiagramDesigner
 
         public override bool OnMouseUp(IInputElement sender, MouseButtonEventArgs e)
         {
-            if (Geometry != null)
-            {
-                Erase(Geometry);
-            }
             return base.OnMouseUp(sender, e);
         }
 
@@ -113,7 +98,7 @@ namespace AIStudio.Wpf.DiagramDesigner
             List<DrawingDesignerItemViewModelBase> deleteDrawGeometries = new List<DrawingDesignerItemViewModelBase>();
             foreach (var g in this.Root.Items.OfType<DrawingDesignerItemViewModelBase>())
             {
-                if (g.Erase(geometry))
+                if (g.Erase(geometry.CloneCurrentValue()))
                     deleteDrawGeometries.Add(g);
                 else
                     empty = false;

AIStudio.Wpf.DiagramDesigner/ViewModels/DrawingViewModel/Erasable/EraserPreviewDrawingDesignerItemViewModel.cs

@@ -0,0 +1,105 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows;
+using System.Windows.Documents;
+using System.Windows.Input;
+using System.Windows.Media;
+using SvgPathProperties;
+
+namespace AIStudio.Wpf.DiagramDesigner
+{
+    public class EraserPreviewDrawingDesignerItemViewModel : DrawingDesignerItemViewModelBase
+    {
+        public EraserPreviewDrawingDesignerItemViewModel()
+        {
+        }
+
+        public EraserPreviewDrawingDesignerItemViewModel(IDiagramViewModel root) : base(root)
+        {
+        }
+
+        public EraserPreviewDrawingDesignerItemViewModel(IDiagramViewModel root, Point startPoint) : base(root, DrawMode.Eraser, startPoint, true)
+        {
+        }
+
+        public EraserPreviewDrawingDesignerItemViewModel(IDiagramViewModel root, List<Point> points) : base(root, DrawMode.Eraser, points, true)
+        {
+        }
+
+        public override bool OnMouseMove(IInputElement sender, MouseEventArgs e)
+        { 
+            if (e.LeftButton == MouseButtonState.Pressed)
+            {
+                var point = e.GetPosition(sender);
+                if (Points == null || Points.Count == 0)//没有起始点
+                {
+                    return true;
+                }
+
+                if ((Points.LastOrDefault() - point).Length < ColorViewModel.LineWidth)
+                {
+                    return true;
+                }
+
+                Points.Add(point);
+                if (Geometry is PathGeometry geometry)
+                {
+
+                }
+                else
+                {
+                    geometry = new PathGeometry();
+                    var figure = new PathFigure { StartPoint = Points[0] };
+                    geometry.Figures.Add(figure);
+                }
+
+                LineSegment arc = new LineSegment(point, true) { IsSmoothJoin = true };
+                geometry.Figures[0].Segments.Add(arc);
+                Geometry = geometry;
+
+                return true;
+            }
+            else
+            {
+                return false;
+            }
+        }
+
+        public override bool OnMouseDown(IInputElement sender, MouseButtonEventArgs e)
+        {
+            return true;
+        }
+
+        public override bool OnMouseUp(IInputElement sender, MouseButtonEventArgs e)
+        {
+            if (Geometry != null)
+            {
+                Erase(Geometry);
+            }
+            return base.OnMouseUp(sender, e);
+        }
+
+        private new bool Erase(Geometry geometry)
+        {
+            var empty = true;
+            List<DrawingDesignerItemViewModelBase> deleteDrawGeometries = new List<DrawingDesignerItemViewModelBase>();
+            foreach (var g in this.Root.Items.OfType<DrawingDesignerItemViewModelBase>())
+            {
+                if (g.Erase(geometry.GetWidenedPathGeometry(new Pen(ColorObject.ToBrush(ColorViewModel.LineColor), ColorViewModel.LineWidth))))
+                    deleteDrawGeometries.Add(g);
+                else
+                    empty = false;
+            }
+
+            foreach (var g in deleteDrawGeometries)
+            {
+                this.Root.Remove(g);
+            }
+
+            return empty;
+        }
+    }
+}