学步园

实现了地图元素的点击选择如图）

   private void axMapControl1_OnMouseDown(object sender, ESRI.ArcGIS.Controls.IMapControlEvents2_OnMouseDownEvent e)
        {
            int m_px = e.x;
            int m_py = e.y;
            IMap m_pMap = axMapControl1.Map;

            ClickSelectFeature(ref m_pMap,m_px,m_py);
        }
        private void ClickSelectFeature( ref IMap m_pMap, int x,int y)
      {        
            // get the layer
            IFeatureLayer pFeatureLayer = m_pMap.get_Layer(0) as IFeatureLayer;
            if (pFeatureLayer == null) return;
            IFeatureClass pFeatureClass = pFeatureLayer.FeatureClass;//get the feature
            if (pFeatureClass == null) return;

            //get mouse position
            IActiveView pActiveView = m_pMap as IActiveView;
            IPoint pPoint = pActiveView.ScreenDisplay.DisplayTransformation.ToMapPoint(x, y);

             //Use a 4 pixel buffer around the cursor for feature search
            double length;
            length = ConvertPixelsToMapUnits(pActiveView, 4);
            ITopologicalOperator pTopo = pPoint as ITopologicalOperator;
            IGeometry pBuffer = pTopo.Buffer(length);//建立4个地图单位的缓冲区
            IGeometry pGeometry =  pBuffer.Envelope;//确定鼠标周围隐藏的选择框

            //新建一个空间约束器
            ISpatialFilter pSpatialFilter;
            IQueryFilter pFilter;

            //设置查询约束条件

            pSpatialFilter = new SpatialFilter();
            pSpatialFilter.Geometry = pGeometry;
          
            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;
                default:
                    break;
            }

            pSpatialFilter.GeometryField = pFeatureClass.ShapeFieldName;
            pFilter = pSpatialFilter;

            //Do the Search 从图层中查询出满足约束条件的元素
            IFeatureCursor pCursor = pFeatureLayer.Search(pFilter, false);
          
            //select
            IFeature pFeature = pCursor.NextFeature();
            m_pMap.SelectFeature(pFeatureLayer, pFeature);          
            while (pFeature != null)
            {
                m_pMap.SelectFeature(pFeatureLayer, pFeature);
                pFeature = pCursor.NextFeature();
            }
           

            pActiveView.PartialRefresh(esriViewDrawPhase.esriViewGeoSelection, null, null);

       }

        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;
        }