重新设计了创建连线时的逻辑，能够预览连接成功后的外观样式

Serein.Workbench.Avalonia/Model/NodeConnectionLine.cs

@@ -0,0 +1,41 @@
+using Avalonia.Controls;
+using Serein.Workbench.Avalonia.Custom.Views;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Serein.Workbench.Avalonia.Model
+{
+
+    /// <summary>
+    /// 绘制的线
+    /// </summary>
+    public class NodeConnectionLine
+    {
+        /// <summary>
+        /// 将线条绘制出来（临时线）
+        /// </summary>
+        /// <param name="canvas">放置画布</param>
+        /// <param name="line">线的实体</param>
+        public NodeConnectionLine(Canvas canvas, ConnectionLineShape line)
+        {
+            Canvas = canvas;
+            Line = line;
+            canvas?.Children.Add(line);
+        }
+
+
+        public Canvas Canvas { get; }
+        public ConnectionLineShape Line { get; }
+
+        /// <summary>
+        /// 移除线
+        /// </summary>
+        public void Remove()
+        {
+            Canvas?.Children.Remove(Line);
+        }
+    }
+}