获取所有图层中选择的feature

            IGeometry polygon;
            IActiveView pActiveView;
            IEnumFeature pEnumFeature;
            IFeature pFeature;
            IFeature pFirstFeature;
            pActiveView = (IActiveView)pMap;

            if (pMap.SelectionCount == 0)
            {
                return;
            }
            pEnumFeature = pMap.FeatureSelection as IEnumFeature;
            pEnumFeature.Reset();
            pFirstFeature = pEnumFeature.Next();
            pFeature = pEnumFeature.Next();