AE要素选择（点选和拉框选择）

选择一个要素或者一个要素集（FeatureSelection）的方法很多，如IMap：：SelectByShape、ILayer：：search、IFeatureSection：：SelectFeature等方法

主要用到的方法：

IMap接口的SelectFeature(Layer, Feature) （方法，从一个Layer中选择一个Feature）；

IMap接口SelectByShape(Shape, env, justOne) （方法，从Layer中依靠一个图形的范围shape和一个选择的环境env来选择要素，而在所有图层中只从IFeatureLayer的图层中进行选择）

IFeatureSelection接口SelectFeatures (Filter, Method, justOne ) （方法，根据指定的标准过滤器filter和方法，选择要素，第一个参数为QueryFilter类型的变量，第二个参数为esriSelectionResultEnum类型的变量，第三个参数为布尔型变量，通常为false）

IFeatureLayer接口Search (IqueryFilter, book ) （方法，创建一个游标去查询相应设置的过滤器的查询）

1 点选法获取要素

   废话少说先看代码：

private double ConvertPixelsToMapUnits(IActiveView pActiveView, double pixelUnits)
        {
            // Uses the ratio of the size of the map in pixels to map units to do the conversion
            IPoint p1 = pActiveView.ScreenDisplay.DisplayTransformation.VisibleBounds.UpperLeft;
            IPoint p2 = pActiveView.ScreenDisplay.DisplayTransformation.VisibleBounds.UpperRight;
            int x1, x2, y1, y2;
            pActiveView.ScreenDisplay.DisplayTransformation.FromMapPoint(p1, out x1, out y1);
            pActiveView.ScreenDisplay.DisplayTransformation.FromMapPoint(p2, out x2, out y2);
            double pixelExtent = x2 - x1;
            double realWorldDisplayExtent = pActiveView.ScreenDisplay.DisplayTransformation.VisibleBounds.Width;
            double sizeOfOnePixel = realWorldDisplayExtent / pixelExtent;
            return pixelUnits * sizeOfOnePixel;
        }
             IMap pMap = axMapControl1.Map;
                IActiveView pActiveView = pMap as IActiveView;
                IFeatureLayer pFeatureLayer = pMap.get_Layer(0) as IFeatureLayer;
                IFeatureClass pFeatureClass = pFeatureLayer.FeatureClass;

                //设置点击点的位置
                IPoint point = pActiveView.ScreenDisplay.DisplayTransformation.ToMapPoint(e.x, e.y);
                ITopologicalOperator pTOpo = point as ITopologicalOperator;
                double length;
                length = ConvertPixelsToMapUnits(pActiveView, 4);
                IGeometry pBuffer = pTOpo.Buffer(length);
                IGeometry pGeomentry = pBuffer.Envelope;
                //空间滤过器
                ISpatialFilter pSpatialFilter = new SpatialFilterClass();
                pSpatialFilter.Geometry = pGeomentry;
                //根据被选择要素的不同，设置不同的空间滤过关系
                switch (pFeatureClass.ShapeType)
                {
                    case esriGeometryType.esriGeometryPoint:
                        pSpatialFilter.SpatialRel=esriSpatialRelEnum.esriSpatialRelContains;
                        break;
                    case esriGeometryType.esriGeometryPolyline:
                        pSpatialFilter.SpatialRel=esriSpatialRelEnum.esriSpatialRelCrosses;
                        break;
                    case esriGeometryType.esriGeometryPolygon :
                        pSpatialFilter.SpatialRel=esriSpatialRelEnum.esriSpatialRelIntersects;
                        break;

                }
                IFeatureSelection pFSelection=pFeatureLayer as IFeatureSelection;
                pFSelection.SelectFeatures(pSpatialFilter,esriSelectionResultEnum.esriSelectionResultNew,false);
                ISelectionSet pSelectionset=pFSelection.SelectionSet;
                ICursor pCursor;
                pSelectionset.Search(null,true,out pCursor);
                IFeatureCursor pFeatCursor=pCursor as IFeatureCursor;
                IFeature pFeature=pFeatCursor.NextFeature();
                 while(pFeature!=null)
                 {
                     pMap.SelectFeature(pFeatureLayer,pFeature);
                     pFeature=pFeatCursor.NextFeature();
                 }
           pActiveView.PartialRefresh(esriViewDrawPhase.esriViewGraphicSelection,null,null);
//另外的改写：
             pSpatialFilter.GeometryField = pFeatureClass.ShapeFieldName;
                IQueryFilter pFilter = pSpatialFilter;
                IFeatureCursor pFeatCursor = pFeatureLayer.Search(pFilter,false);
                IFeature pFeature=pFeatCursor.NextFeature();
                 while(pFeature!=null)
                 {
                     pMap.SelectFeature(pFeatureLayer,pFeature);
                     pFeature=pFeatCursor.NextFeature();
                 }
           pActiveView.PartialRefresh(esriViewDrawPhase.esriViewGraphicSelection,null,null);

另外还有一种比较简单的点选方法：

 IGeometry g = null;
                IEnvelope pEnv;
                IActiveView pActiveView = axMapControl1.ActiveView;
                IMap pMap = axMapControl1.Map;
                pEnv = axMapControl1.TrackRectangle();
                if (pEnv.IsEmpty == true)
                {
                    ESRI.ArcGIS.Display.tagRECT r;
                    r.bottom = e.y + 5;
                    r.top = e.y - 5;
                    r.left = e.x - 5;
                    r.right = e.x + 5;
                    pActiveView.ScreenDisplay.DisplayTransformation.TransformRect(pEnv, ref r, 4);
                    pEnv.SpatialReference = pActiveView.FocusMap.SpatialReference;
                }
                g = pEnv as IGeometry;
                axMapControl1.Map.SelectByShape(g, null, false);
                axMapControl1.Refresh(esriViewDrawPhase.esriViewGeoSelection, null, null);

2 拉框选择

 IMap pMap = axMapControl1.Map;
                IActiveView pActiveView = pMap as IActiveView;
                IEnvelope pEnv = axMapControl1.TrackRectangle();
                pMap.SelectByShape(pEnv, null, false);
                pActiveView.PartialRefresh(esriViewDrawPhase.esriViewGeoSelection,null, null);