添加Avalonia项目的demo

Serein.Workbench.Avalonia/Extension/PointExtension.cs

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+using Avalonia;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Serein.Workbench.Avalonia.Extension
+{
+    public static class PointExtension
+    {
+        public static Point Add(this Point a, Point b)
+        {
+            return new Point(a.X + b.X, a.Y + b.Y);
+        }
+
+        public static Point Sub(this Point a, Point b)
+        {
+            return new Point(a.X - b.X, a.Y - b.Y);
+        }
+
+        public static Vector ToVector(this Point me)
+        {
+            return new Vector(me.X, me.Y);
+        }
+    }
+    public static class VectorExtension
+    {
+        public static double DotProduct(this Vector a, Vector b)
+        {
+            return a.X * b.X + a.Y * b.Y;
+        }
+
+        public static Vector NormalizeTo(this Vector v)
+        {
+            var temp = v;
+            temp.Normalize();
+
+            return temp;
+        }
+    }
+}