点选功能的实现，对于sharpMap v0.9来说，几乎没有涉及到空间分析的方法，比如多边形的相交，点在哪个多边形内等，如果要完成这些功能，可以借助NetTopologySuite和GeoAPI两个开源项目的成果。但值得庆幸的是即将推出的sharpMap v2.0，将对以上的几个开源项目进行集成，使SharpMap具有了空间分析功能。此点选功能的实现也是借助了NetTopologySuite和GeoAPI。效果图如下：
代码如下：
 System.Drawing.PointF pt_click = new PointF((float)e.X, (float)e.Y);
SharpMap.Geometries.Point pt_map = szmap.ImageToWorld(pt_click);
//获取图层
SharpMap.Layers.VectorLayer query_lyr = szmap.GetLayerByName("深圳区域shp.shp") as SharpMap.Layers.VectorLayer;
if (query_lyr == null) return;
//查询和鼠标点击的点相交的要素
SharpMap.Data.FeatureDataSet ds = new SharpMap.Data.FeatureDataSet();
if (!query_lyr.DataSource.IsOpen) query_lyr.DataSource.Open();
query_lyr.DataSource.ExecuteIntersectionQuery(pt_map.GetBoundingBox(), ds);
 query_lyr.DataSource.Close();
if (ds == null) return;
//利用NetTopologySuite和GeoAPI
GisSharpBlog.NetTopologySuite.IO.WKTReader reader = new GisSharpBlog.NetTopologySuite.IO.WKTReader();
GeoAPI.Geometries.IGeometry point = reader.Read(pt_map.ToString());
//获取第一个要素和点击点的距离
int rowid = 0;
SharpMap.Data.FeatureDataTable dt = ds.Tables[0] as SharpMap.Data.FeatureDataTable ;
if (dt == null) return;
SharpMap.Data.FeatureDataRow dr1 = dt[0] as SharpMap.Data.FeatureDataRow;
double distance = point.Distance(reader.Read(dr1.Geometry.ToString()));
//若表中的要素大于1则要进行距离比较
int rowcount=0;
foreach(SharpMap.Data.FeatureDataRow r in dt )
{
rowcount++;
}
if (rowcount>1)
{
for (int i = 1; i <rowcount; i++)
{
SharpMap.Data.FeatureDataRow dr = dt[i] as SharpMap.Data.FeatureDataRow;
if (distance > point.Distance(reader.Read(dr.Geometry.ToString())))
{
distance = point.Distance(reader.Read(dr.Geometry.ToString()));
rowid = i;
}
}
}
//将选中的要素存入session中,以进行缓冲分析
Session.Add("selectedFeature", dt[rowid].Geometry);
//把选中要素添加到选择图层，高亮显示
SharpMap.Layers.VectorLayer selectedLyr = new SharpMap.Layers.VectorLayer("selectedLyr");
selectedLyr.DataSource = new SharpMap.Data.Providers.GeometryProvider(dt[rowid ] as SharpMap.Data.FeatureDataRow );
selectedLyr.Style.EnableOutline = true;
selectedLyr.Style.Outline = new Pen(Color.Blue, 2);
selectedLyr.Style.Fill = new SolidBrush(Color.Transparent);
selectedLyr.SRID = 4326;
szmap.Layers.Add(selectedLyr);
此代码实现了通过鼠标点击，在地图上高亮所选地图要素。
不过在对准确性要求不高的情况下，可以只借助sharpMap本身提供的ExecuteIntersectionQuery方法来获取结果 System.Drawing.PointF pt_click = new PointF((float)e.X, (float)e.Y);
SharpMap.Geometries.Point pt_map = szmap.ImageToWorld(pt_click);
//获取图层
SharpMap.Layers.VectorLayer query_lyr = szmap.GetLayerByName("深圳区域shp.shp") as SharpMap.Layers.VectorLayer;
if (query_lyr == null) return;
//查询和鼠标点击的点相交的要素
SharpMap.Data.FeatureDataSet ds = new SharpMap.Data.FeatureDataSet();
if (!query_lyr.DataSource.IsOpen) query_lyr.DataSource.Open();
query_lyr.DataSource.ExecuteIntersectionQuery(pt_map.GetBoundingBox(), ds);
query_lyr.DataSource.Close();
//把选中要素添加到选择图层，高亮显示
SharpMap.Layers.VectorLayer selectedLyr = new SharpMap.Layers.VectorLayer("selectedLyr");
selectedLyr.DataSource = new SharpMap.Data.Providers.GeometryProvider(ds.Tables[0] as SharpMap.Data.FeatureDataTable);
selectedLyr.Style.EnableOutline = true;
selectedLyr.Style.Outline = new Pen(Color.Blue, 2);
selectedLyr.Style.Fill = new SolidBrush(Color.Transparent);
selectedLyr.SRID = 4326;
szmap.Layers.Add(selectedLyr); 此中方法准确性就不是很高，在几个地物相邻处点击鼠标，往往要选中几个地图要素，这是由于它是分析地图要素的boundingBox的空间关系来获取的。
powered by sharpMap v0.9,NetTopologySuite,GeoAPI.
代码参考了网上一些资料和www.sharpgis.net 转载于:https://www.cnblogs.com/liujunhzau524/archive/2008/07/08/1238047.html |
