ArcEngine中线要素自相交的判断及打断

接着上一篇博客，这篇还是讲线要素的打断~线要素有时会出现线段自相交的情况，如下图所示，该shp文件中有3条要素自相交。
那么如何快速找到自相交的要素呢？方法一基本上学过ArcGIS的都能想到，那就是导入要素数据集，进行相应的拓扑检查。另一个方法就是利用ITopologicalOperator3接口进行检查，看下面这段代码：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using ESRI.ArcGIS.Carto;
using ESRI.ArcGIS.Controls;
using ESRI.ArcGIS.DataSourcesFile;
using ESRI.ArcGIS.DataSourcesGDB;
using ESRI.ArcGIS.Display;
using ESRI.ArcGIS.esriSystem;
using ESRI.ArcGIS.Geodatabase;
using ESRI.ArcGIS.Geometry;
using ESRI.ArcGIS.Output;
using ESRI.ArcGIS.SystemUI;namespace WindowsFormsApplication1
{public partial class Form1 : Form{public Form1(){InitializeComponent();axMapControl1.LoadMxFile(@"C:\Users\DSF\Desktop\data\无标题.mxd");}private void button1_Click(object sender, EventArgs e){IFeatureLayer pFeatureLayer = axMapControl1.get_Layer(0) as IFeatureLayer;SelectSelfIntersectionsFeatures(pFeatureLayer);}private void SelectSelfIntersectionsFeatures(IFeatureLayer pFeatureLayer){IFeatureClass pFeatureClass = pFeatureLayer.FeatureClass;IFeatureCursor pFeatureCursor = pFeatureClass.Search(null, true);IFeature pFeature = pFeatureCursor.NextFeature();if (pFeature == null){return;}// 遍历线要素StringBuilder builder = new StringBuilder();while (pFeature != null){ITopologicalOperator3 pTopologicalOperator3 = pFeature.ShapeCopy as ITopologicalOperator3;pTopologicalOperator3.IsKnownSimple_2 = false;// 检查自相交esriNonSimpleReasonEnum reason = esriNonSimpleReasonEnum.esriNonSimpleOK;if (!pTopologicalOperator3.get_IsSimpleEx(out reason)){if (reason == esriNonSimpleReasonEnum.esriNonSimpleSelfIntersections){builder.Append("FID=" + pFeature.OID.ToString() + " or ");}}pFeature = pFeatureCursor.NextFeature();}System.Runtime.InteropServices.Marshal.ReleaseComObject(pFeatureCursor);builder.Remove(builder.Length - 3, 3);// 创建属性过滤器IQueryFilter pQueryFilter = new QueryFilter();pQueryFilter.AddField("FID");pQueryFilter.WhereClause = builder.ToString();// 查询自相交要素IFeatureSelection pFeatureSelection = pFeatureLayer as IFeatureSelection;pFeatureSelection.SelectFeatures(pQueryFilter, esriSelectionResultEnum.esriSelectionResultNew, false);axMapControl1.ActiveView.PartialRefresh(esriViewDrawPhase.esriViewGeoSelection, null, null);}}
}

这段代码的核心就是IsKnownSimple_2和get_IsSimpleEx，前者设置为false，就是假设当前要素不是一个简单要素，然后调用get_IsSimpleEx，判断当前要素是否为自相交要素，运行结果如下所示，通过这段代码就能查询出自相交的要素。
在找出自相交的要素后如何在其自相交处对线进行打断呢？前一篇博客介绍了IFeatureEdit接口，但在这种情况下并不适用，因此我们考虑使用IGeometryCollection接口来做，代码如下：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using ESRI.ArcGIS.Carto;
using ESRI.ArcGIS.Controls;
using ESRI.ArcGIS.DataSourcesFile;
using ESRI.ArcGIS.DataSourcesGDB;
using ESRI.ArcGIS.Display;
using ESRI.ArcGIS.esriSystem;
using ESRI.ArcGIS.Geodatabase;
using ESRI.ArcGIS.Geometry;
using ESRI.ArcGIS.Output;
using ESRI.ArcGIS.SystemUI;namespace WindowsFormsApplication1
{public partial class Form1 : Form{public Form1(){InitializeComponent();axMapControl1.LoadMxFile(@"C:\Users\DSF\Desktop\data\无标题.mxd");}private void button1_Click(object sender, EventArgs e){IFeatureLayer pFeatureLayer = axMapControl1.get_Layer(1) as IFeatureLayer;IFeatureClass pFeatureClass = pFeatureLayer.FeatureClass;List<IPolyline> list = GetSelfIntersectionsPolyline(axMapControl1.get_Layer(0) as IFeatureLayer);for (int i = 0; i < list.Count; i++){IFeature pFeature = pFeatureClass.CreateFeature();pFeature.Shape = list[i];pFeature.Store();}}private List<IPolyline> GetSelfIntersectionsPolyline(IFeatureLayer pFeatureLayer){IFeatureClass pFeatureClass = pFeatureLayer.FeatureClass;IFeatureCursor pFeatureCursor = pFeatureClass.Search(null, true);IFeature pFeature = pFeatureCursor.NextFeature();if (pFeature == null){return null;}// 遍历线要素List<IPolyline> list = new List<IPolyline>();object missing = Type.Missing;while (pFeature != null){ITopologicalOperator3 pTopologicalOperator3 = pFeature.ShapeCopy as ITopologicalOperator3;pTopologicalOperator3.IsKnownSimple_2 = false;// 检查自相交esriNonSimpleReasonEnum reason = esriNonSimpleReasonEnum.esriNonSimpleOK;if (!pTopologicalOperator3.get_IsSimpleEx(out reason)){if (reason == esriNonSimpleReasonEnum.esriNonSimpleSelfIntersections){pTopologicalOperator3.Simplify();IGeometryCollection pGeometryCollection = pTopologicalOperator3 as IGeometryCollection;for (int i = 0; i < pGeometryCollection.GeometryCount; i++){IGeometryCollection pPolyline = new Polyline() as IGeometryCollection;pPolyline.AddGeometry(pGeometryCollection.get_Geometry(i), ref missing, ref missing);list.Add(pPolyline as IPolyline);}}}pFeature = pFeatureCursor.NextFeature();}// 返回结果System.Runtime.InteropServices.Marshal.ReleaseComObject(pFeatureCursor);return list;}}
}

结果如下：