使用AO无法获得地图比例尺的原因

今天使用AO求地图比例尺，一直求不出来，最终发现原因是地图没有设定单位，即mapUnit属性。<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

pMap = pHookHelper.FocusMap;

pWorkspaceFactory = new ShapefileWorkspaceFactoryClass();

pFeatureLayer = new FeatureLayerClass();

pFeatureWorkspace = (IFeatureWorkspace)pWorkspaceFactory.OpenFromFile(Path.GetDirectoryName(openFileDialog.FileName), 0);

pFeatureLayer.FeatureClass = pFeatureWorkspace.OpenFeatureClass(Path.GetFileName(openFileDialog.FileName));

//这句话必须加上，否则该Layer名字将为“”，TOCContronl内的名称也不显示！

pFeatureLayer.Name = pFeatureLayer.FeatureClass.AliasName;

pMap.AddLayer(pFeatureLayer);

pMap.MapUnits = ESRI.ArcGIS.esriSystem.esriUnits.esriMeters;//必须设定单位，否则比例尺无法计算

((IActiveView)pMap).Refresh();