Visual.VisualEdgeMode屬性可以爲派生類設置，但不能作爲類成員設置

Question

在下面的代碼中，我的LineAliased和LineAntiAliased類派生自DrawingVisual，我可以使用「this」關鍵字來設置「VisualEdgeMode」屬性爲每個班級。這工作正常，我可以按預期的方式將畫線繪製到畫布上，其中一行是別名，一行是AntiAliased。

但是，在我的Lines類中，我不是從DrawingVisual派生的，而是爲該類創建DrawingVisual成員。

問題是，當我嘗試爲這些成員設置「VisualEdgeMode」屬性時，出現「System.Windows.Media.Visual.VisualEdgeMode由於其保護級別而無法訪問」的錯誤。

我很新，一直沒有找到一個體面的解釋我在做什麼錯了，爲什麼這是行不通的。

Visual.VisualEdgeMode財產上的MSDN
http://msdn.microsoft.com/en-us/library/system.windows.media.visual.visualedgemode(v=vs.110).aspx

DrawingVisual類MSDN上
http://msdn.microsoft.com/en-us/library/system.windows.media.drawingvisual(v=vs.110).aspx

THANK YOU！

using System; 
using System.Windows.Media; 
using System.Windows.Controls; 
using System.Windows; 

namespace CanvasTest 
{ 
    public class LineAliased : DrawingVisual 
    { 
     public LineAliased() 
     { 
      this.VisualEdgeMode = EdgeMode.Aliased; 
      DrawingContext dc = this.RenderOpen(); 
      dc.DrawLine(new Pen(new SolidColorBrush(Colors.Red), 1), new Point(100, 105), new Point(300, 105)); 
      dc.Close(); 
     } 
    } 

    public class LineAntiAliased : DrawingVisual 
    { 
     public LineAntiAliased() 
     { 
      this.VisualEdgeMode = EdgeMode.Unspecified; 
      DrawingContext dc = this.RenderOpen(); 
      dc.DrawLine(new Pen(new SolidColorBrush(Colors.Red), 1), new Point(100, 100), new Point(300, 100)); 
      dc.Close(); 
     } 
    } 

    public class Lines 
    { 
     public DrawingVisual objDrawingVisualAliased = new DrawingVisual(); 
     public DrawingVisual objDrawingVisualAntiAliased = new DrawingVisual(); 

     public Lines() 
     { 
      // Next line gives following error. 
      // System.Windows.Media.Visual.VisualEdgeMode is inaccessible due to its protection level. 
      objDrawingVisualAliased.VisualEdgeMode = EdgeMode.Aliased; 
      DrawingContext dc1 = objDrawingVisualAliased.RenderOpen(); 
      dc1.DrawLine(new Pen(new SolidColorBrush(Colors.Red), 1), new Point(100, 105), new Point(300, 105)); 
      dc1.Close(); 

      // Next line gives following error. 
      // System.Windows.Media.Visual.VisualEdgeMode is inaccessible due to its protection level. 
      objDrawingVisualAntiAliased.VisualEdgeMode = EdgeMode.Unspecified; 
      DrawingContext dc2 = objDrawingVisualAntiAliased.RenderOpen(); 
      dc2.DrawLine(new Pen(new SolidColorBrush(Colors.Red), 1), new Point(100, 105), new Point(300, 105)); 
      dc2.Close(); 
     } 
    } 

    public class DrawingCanvas : Canvas 
    { 
     // This object is used to work with the Visuals belonging to the Canvas. 
     private VisualCollection graphicsList; 

     public DrawingCanvas() 
     { 
      graphicsList = new VisualCollection(this); 
      graphicsList.Add(new LineAliased()); 
      graphicsList.Add(new LineAntiAliased()); 


      Lines lines = new Lines(); 
      graphicsList.Add(lines.objDrawingVisualAliased); 
      graphicsList.Add(lines.objDrawingVisualAntiAliased); 
     } 

     // http://msdn.microsoft.com/en-us/library/ms742254.aspx#creating_overrides 
     // Provide required overrides 
     protected override int VisualChildrenCount { get { return graphicsList.Count; } } 
     protected override Visual GetVisualChild(int index) 
     { 
      if (index < 0 || index >= graphicsList.Count) { throw new ArgumentOutOfRangeException(); } 
      return graphicsList[index]; 
     } 

    } 
} 

Answer 1

的VisualEdgeMode屬性是protected，因此是從派生類（或定義類本身）的方法僅入店。

您可以但是調用靜態RenderOptions.SetEdgeMode代替：

RenderOptions.SetEdgeMode(objDrawingVisualAliased, EdgeMode.Aliased);