DotSpatial 要素合并

private void toolStripButton45_Click(object sender, EventArgs e)
        {
            //存在Bug，合并丢失现象
            if (mapMain.Layers.Count == 0)
            {
                return;
            }
            //查看与选中要素重叠的要素
            PolygonLayer pLayer = Lzq_LayerManager.getLayerByName(layerNamePolygon, mapMain) as PolygonLayer;
            if (pLayer == null)
            {
                MessageBox.Show(@"未找到具体图层：" + layerNamePolygon, @"系统提示", MessageBoxButtons.OK, MessageBoxIcon.Error);
                return;
            }

            FeatureSet fs = null;
            fs = (FeatureSet)pLayer.DataSet; ;
            if (pLayer.Selection.Count <2)
            {
                MessageBox.Show(@"图层至少要选中两个要素：" + pLayer.Selection.Count, @"系统提示", MessageBoxButtons.OK, MessageBoxIcon.Error);
                return;
            }

            //防止有合并后有悬挂线，先将面图元进行正值缓冲，合并后，将图元负值缓冲

            double buffer = 0.001; //容差
            ////获取第一个被选中要素
            IFeature pFeature = (Feature)pLayer.Selection.ToFeatureList()[0];
            NetTopologySuite.Geometries.Geometry gm1 = (NetTopologySuite.Geometries.Geometry)pFeature.Geometry;
            Geometry g1 = (Geometry)pFeature.Geometry.Clone();
            Geometry g1Buff = (Geometry)g1.Buffer(buffer);

            //遍历选择级，找到重叠要素
            for (int j = 1; j < pLayer.Selection.Count; j++)
            {
                IFeature pFeature2 = (Feature)pLayer.Selection.ToFeatureList()[j];
                Geometry gm2 = (Geometry)pFeature2.Geometry.Clone();
                CoordinateArrays.RemoveRepeatedPoints(gm2.Coordinates);
                Geometry gm2Buff = (Geometry)gm2.Buffer(buffer);
                Geometry p = (Geometry)g1Buff.Union(gm2Buff);
                Console.WriteLine(p.IsSimple.ToString());
                if (p.IsSimple)
                {
                    CoordinateArrays.RemoveRepeatedPoints(p.Coordinates);
                    p.Normalize();
                    pFeature.Geometry = p.Buffer(-1 * buffer);
                    fs.Features.Remove(pFeature2);
                    ClassBase.IndexError(pLayer, mapMain);
                }
            }
            fs.Save();
        }

        public static void IndexError(DotSpatial.Symbology.IFeatureLayer fLayer, DotSpatial.Controls.Map _map)
        {
            fLayer.DataSet.UpdateExtent();
            fLayer.DataSet.InitializeVertices();
            if (fLayer.LabelLayer != null)
            {
                fLayer.LabelLayer.CreateLabels();
            }

            fLayer.AssignFastDrawnStates();

            if (_map != null)
            {
                _map.Refresh();
                _map.ResetBuffer();
            }
        }

        public static Layer getLayerByName(string layerName, Map mainMap)
        {
            Layer layer = null;
            foreach (FeatureLayer featureLayer in mainMap.Layers)
            {
                if (featureLayer.Name == layerName)
                {
                    layer = featureLayer;
                }
            }
            return layer;
        }

　　选中两个以上元素，只能合并两个，目前没解决此处bug，应该是

ClassBase.IndexError(pLayer, mapMain);操作后将selection 清空导致，有研究过的帮忙 解答一下，谢谢！

原文地址：https://www.cnblogs.com/kogame/p/12503582.html