[求助] 求救!VB.net + MapX5.02 为何我无法添加图元

<P>Dim f As New MapXLib.Feature<BR>f.Attach(AxMap1)<BR>f.Type = MapXLib.FeatureTypeConstants.miFeatureTypeSymbol<BR>f.Point.Set(AxMap1.CenterX, AxMap1.CenterY)<BR>AxMap1.Layers(1).AddFeature(f)</P>
<P>为何老报:</P>
<P>未处理的“System.Runtime.InteropServices.COMException”类型的异常出现在 mscorlib.dll 中。</P>
<P>其他信息: Unable to attach Feature to the map. Make sure Map object is valid.</P>
<P>为何Map object会无效.请高人相助。</P>