ArcGIS Engine识别要素：要素识别功能实现

在arcgismap中，我们点击 识别 要素的按钮，然后在选中元素就可以获取这个要素的属性了。

在arcgisengine中，实现的 原理 如下：

获取鼠标点击 位置信息

如果是栅格图层：

图层转为Identify对象，将扩大后的点作为参数输入，进行识别

遍历识别结果记录，获取图层名和对应位置的属性值

如果是 矢量 要素图层：

先对点进行缓冲，扩大点覆盖范围（尽量减少 对空白区域的识别，增加对有效记录的识别）

图层转为Identify对象，将扩大后的点作为参数输入，进行识别

遍历识别结果中的记录，获取对应的要素属性记录，通过遍历属性记录来获取属性记录的字段、字段名
代码 参考：

 #region 双击识别        private void axMapControl1_OnDoubleClick(object sender, IMapControlEvents2_OnDoubleClickEvent e)        {            //获取鼠标点击位置点            IPoint point = new PointClass();            point.PutCoords(e.mapX, e.mapY);            string output = "";            for (int i = 0; i < axMapControl1.LayerCount; i++)            {                output += Identify_layer(axMapControl1.get_Layer(i), point);            }            MessageBox.Show(output);        }        private string Identify_layer(ILayer layer, IPoint SelectedPoint)        {            //定义几何图形            IGeometry pGeometry;            //定义结果字符串            string output = "";            //如果是矢量图层            if (layer is IFeatureLayer)            {                //图层转Identify对象                IIdentify pFL = layer as IIdentify;                //对点进行缓冲赋给几何图形，尽量减少对空白区域判定                ITopologicalOperator pTopo = SelectedPoint as ITopologicalOperator;                pGeometry = pTopo.Buffer(500);                //将几何图形作为输入传入Identify对象，进行识别                IArray id_result = pFL.Identify(pGeometry);                if (id_result != null)                {                    //对识别结果中的记录进行遍历（由于缓冲扩大，可能识别到同一图层多条记录）                    for (int i = 0; i < id_result.Count; i++)                    {                        //获取识别结果记录中的属性记录                        IIdentifyObj featureIdentifyobj = (IIdentifyObj)id_result.get_Element(i);                        IRowIdentifyObject iRowIdentifyObject = featureIdentifyobj as IRowIdentifyObject;                        IRow pRow = iRowIdentifyObject.Row;//添加引用GeoDatabase                        output += "\"" + featureIdentifyobj.Layer.Name + "\":\n";                        //遍历属性记录，获取字段名、字段值                        for (int a = 0; a < pRow.Fields.FieldCount; a++)                        {                            if (pRow.Fields.get_Field(a).Type != esriFieldType.esriFieldTypeGeometry)                            {                                output += String.Format("{0}={1} \n", pRow.Fields.get_Field(a).Name, pRow.get_Value(a).ToString());                            }                        }                    }                }            }            else if (layer is IRasterLayer)            {                //图层转Identify对象                IIdentify pFL = layer as IIdentify;                //点转几何对象                pGeometry = SelectedPoint as IGeometry;                //将几何图形作为输入传入Identify对象，进行识别                IArray id_result = pFL.Identify(pGeometry);                if (id_result != null)                {                    //遍历识别结果记录，获取图层名和对应位置的属性值                    for (int i = 0; i < id_result.Count; i++)                    {                        IIdentifyObj featureIdentifyobj = (IIdentifyObj)id_result.get_Element(i);                        IRasterIdentifyObj rasterIdentifyobj = featureIdentifyobj as IRasterIdentifyObj;                        output += "\"" + featureIdentifyobj.Layer.Name + "\":" + "\n" + rasterIdentifyobj.MapTip + "\n";                    }                }            }             return output + "\n";        }        #endregion

参考代码2：

1                         ITopologicalOperator pTopo; 2                         IGeometry pGeometry; 3                         IFeature pFeature; 4                         IFeatureLayer pFeatureLayer; 5                         IFeatureCursor pCursor; 6                         ISpatialFilter pFilter; 7                         DataTable dataTable; 8                          9                         for (int i = 0; i < axMapControl1.Map.LayerCount; i++)10                         {11                             12                             pPoint = new PointClass();13                             pPoint.PutCoords(e.mapX, e.mapY);14                             pTopo = pPoint as ITopologicalOperator;17                             double m_Radius = 1;18                             pGeometry = pTopo.Buffer(m_Radius); 19                             if (pGeometry == null)20                                 continue;21                             axMapControl1.Map.SelectByShape(pGeometry, null, true);//第三个参数为是否只选中一个22                             axMapControl1.Refresh(esriViewDrawPhase.esriViewGeoSelection, null, null); //选中要素高亮显示23                             pFilter = new SpatialFilterClass();25                             pFilter.SpatialRel = esriSpatialRelEnum.esriSpatialRelIntersects;26                             pFilter.Geometry = pGeometry;27                             pFeatureLayer = axMapControl1.Map.get_Layer(i) as IFeatureLayer; 28                             pCursor = pFeatureLayer.Search(pFilter, false);29                             pFeature = pCursor.NextFeature();30                             string fieldName;31                             if (pFeature != null)33                             {34                                 if (Application.OpenForms["otherQueryForm"] == null)35                                 {36                                     otherqueryform = new otherQueryForm();37                                     otherqueryform.Show();38                                 }39                                 else40                                 {41                                     Application.OpenForms["otherQueryForm"].Show();42                                 }//这里主要控制子窗体不会重复弹出44                                 dataTable = new DataTable();45                                 for (int k = 0; k < 2; k++)46                                 {47                                     if (k == 0)48                                     {49                                         dataTable.Columns.Add("属性");50                                     }51                                     if (k == 1)52                                     {53                                         dataTable.Columns.Add("值");54                                     }55                                 }56                                 DataRow datarow;57                                 for (int j = 0; j < pFeature.Fields.FieldCount; j++)58                                 {59                                     datarow = dataTable.NewRow();60                                     for (int m = 0; m < 2; m++)61                                     {62                                         if (m == 0)63                                         {64                                             fieldName = pFeature.Fields.get_Field(j).Name;65                                             datarow[m] = fieldName;66                                         }67                                         if (m == 1)68                                         {69                                             if (pFeature.Fields.get_Field(j).Name == "Shape")70                                             {71                                                 if (pFeature.Shape.GeometryType == ESRI.ArcGIS.Geometry.esriGeometryType.esriGeometryPoint)72                                                 {73                                                     datarow[m] = "点";74                                                 }75                                                 if (pFeature.Shape.GeometryType == ESRI.ArcGIS.Geometry.esriGeometryType.esriGeometryPolyline)76                                                 {77                                                     datarow[m] = "线";78                                                 }79                                                 if (pFeature.Shape.GeometryType == ESRI.ArcGIS.Geometry.esriGeometryType.esriGeometryPolygon)80                                                 {81                                                     datarow[m] = "面";82                                                 }83                                             }84                                             else85                                             {86                                                 datarow[m] = pFeature.get_Value(j).ToString();87                                             }88                                         }89                                     }90                                     dataTable.Rows.Add(datarow);91                                 }92                                 otherqueryform.dataGridView1.DataSource = dataTable;93                                 otherqueryform.layerName_dev.Text = pFeatureLayer.Name;94                                 otherqueryform.dataGridView1.Refresh();95                                 pFeature = null;96                                 break;97                             }99                         }

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