在ArcGis Engine中实现对符号的预览，生成预览图片。使用的时候只要调用SymbolToBitmp(符号，宽，高)就可以返回生成的图片了。关键代码如下：

public System.Drawing.Bitmap SymbolToBitmp(ESRI.ArcGIS.Display.ISymbol pSymbol,int iwidth,int iheight)
{   
 //根据高宽创建图象
 Bitmap bmp = new Bitmap(iwidth,iheight);
 Graphics gImage = Graphics.FromImage(bmp);
 gImage.Clear(Color.White);
 double dpi = gImage.DpiX;

 IEnvelope pEnvelope = new EnvelopeClass();
 pEnvelope.PutCoords(0,0,(double)bmp.Width,(double)bmp.Height);

 tagRECT deviceRect;   
 deviceRect.left = 0;
 deviceRect.right = bmp.Width;
 deviceRect.top = 0;
 deviceRect.bottom = bmp.Height;   

 IDisplayTransformation pDisplayTransformation = new DisplayTransformationClass();
 pDisplayTransformation.VisibleBounds = pEnvelope;
 pDisplayTransformation.Bounds = pEnvelope;
 pDisplayTransformation.set_DeviceFrame(ref deviceRect);
 pDisplayTransformation.Resolution = dpi;
 
 IGeometry pGeo = CreateSymShape(pSymbol,pEnvelope);

 System.IntPtr hdc = new IntPtr();
 hdc = gImage.GetHdc();

 //将符号的形状绘制到图象中
 pSymbol.SetupDC((int)hdc,pDisplayTransformation);
 pSymbol.Draw(pGeo);
 pSymbol.ResetDC();
 gImage.ReleaseHdc(hdc);      
 gImage.Dispose();

 return bmp;
 
}

public ESRI.ArcGIS.Geometry.IGeometry CreateSymShape(ISymbol pSymbol,IEnvelope pEnvelope)
{// 根据传入的符号以及外包矩形区域返回对应的几何空间实体（点，线、面）
 //判断是否为“点”符号
 ESRI.ArcGIS.Display.IMarkerSymbol IMarkerSym;
 IMarkerSym = pSymbol as IMarkerSymbol;
 if (IMarkerSym != null)
 {
  // 为“点”符号则返回IEnvelope的中心点
  IArea pArea ;
  pArea = pEnvelope as IArea;
  return pArea.Centroid as IGeometry;
 }
 else
 {
  //判断是否为“线”符号
  ESRI.ArcGIS.Display.ILineSymbol IlineSym;
  ESRI.ArcGIS.Display.ITextSymbol ITextSym;
  IlineSym = pSymbol as ILineSymbol;
  ITextSym = pSymbol as ITextSymbol;
  if(IlineSym != null || ITextSym != null)
  {
   //返回45度的对角线
   ESRI.ArcGIS.Geometry.IPolyline IpLine;
   IpLine = new PolylineClass();
   IpLine.FromPoint = pEnvelope.LowerLeft;
   IpLine.ToPoint  = pEnvelope.UpperRight;
   return IpLine as IGeometry;
  }
  else
  {
   //直接返回一个IEnvelope矩形区域
   return pEnvelope as IGeometry;
  }
 }   
}