C#AE练习（5）查询与选择 QueryFilter、SpatialFilter、Select Cities

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我是靠谱客的博主拉长小熊猫，最近开发中收集的这篇文章主要介绍C#AE练习（5）查询与选择 QueryFilter、SpatialFilter、Select Cities，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

要求：

编写程序，使用QueryFilter、SpatialFilter和FeatureCursor。
在这里插入图片描述

1、在Country图层中，以"LANDLOCKED = ‘Y’"为条件进行查询，并对查询结果汇总Country的个数及面积之和。
2、在Country中先选中一个Country（例如Brazil），而后以"Population > 2000000"为条件查询该Country中的所有Cities，统计其个数。
3、将2中满足条件的Cities置于被选中状态。

对象模型图：
在这里插入图片描述

作答：

.1.QueryFilter：

在Country图层中，以“LANDLOCKED = ‘Y’”为条件进行查询，并对查询结果汇总Country的个数及面积之和

//自定义方法FindLayer()，通过查询要素图层名来返回其相应的在地图中的索引值LayerIndex
public int FindLayer(string LayerName)
{
	int i = 0;
	for (; i < axMapControl1.LayerCount; i++)
	{
		if (axMapControl1.get_Layer(i).Name == LayerName)
			break;			
	}
	return i;
}

// QueryFilter
private void button1_Click(object sender, EventArgs e)
{
	if (axMapControl1.Map.LayerCount != 0)
	{
		int LayerIndex = FindLayer("Country"); //自定义方法FindLayer()
		IFeatureLayer pFL = axMapControl1.get_Layer(LayerIndex) as IFeatureLayer;
		IFeatureClass pFC = pFL.FeatureClass;
	
		//创建QueryFilter
		//☆Search cursor查询要素图层FeatureLayer的要素类FeatureClass表中满足属性条件的结果(只是查询，没有返回结果)
		IQueryFilter pQF = new QueryFilterClass();
		pQF.WhereClause = "LANDLOCKED = 'Y'"; //☆设置属性查询条件，根据情况更改
		
		//使用IFeatureClass的Search方法从QueryFilter返回查询结果FeatureCursor(查询结果用FeatureCursor返回了)
		IFeatureCursor pFCur = pFC.Search(pQF, true);
		//☆当FeatureCursor通过Search方法创建后，将建立一个游标(指针)指向首条记录的上面一位。要想获得第一条记录，就要采用NextFeature方法。
       //☆继续调用NextFeature()方法，仍会移动游标(指针)到FeatureCursor的下一条记录，返回相应的Feature
       IFeature pFea = pFCur.NextFeature(); //建立要素访问游标
       	
       	int FieldIndex = pFC.FindField("shape_Area"); //面积字段索引值
       	int Count = 0; //查询的Country的个数
       	double SumArea = 0; //查询的Country的面积之和
	
		while (pFea != null)
		{
			string str = pFea.get_Value(FieldIndex).ToString();
			SumArea += double.Parse(str);
				
			pFea = pFCur.NextFeature();
				
			Count++;			
		}	
		SumArea *= 0.001 * 0.001;  //转换为km²
		MessageBox.Show("总面积：" + SumArea.ToString() +" km² n" + "总数:" + Count.ToString());
	}
}

2.点选提示信息，SpatialFilter

//选择面图层并显示所选择的图层国家名称
private void axMapControl1_OnMouseDown(object sender, IMapControlEvents2_OnMouseDownEvent e)
{
	//-------------------点选-----------------------//
	//创建鼠标点击的位置Point
	IPoint pPoint = new PointClass();
	pPoint.PutCoords(e.mapX, e.mapY);
	
	//创建缓冲区
	ITopologicalOperator pTO = pPoint as ITopologicalOperator;
	IGeometry pGeometry = pTO.Buffer(0);
	
	axMapControl1.Map.SelectByShape(pGeometry, null, false);
	axMapControl1.Refresh(esriViewDrawPhase.esriViewGeoSelection, null, null);
	//--------------------------------------------
		
	/---------------访问Map中FeatureLayer被选中的要素---------------///
	int LayerIndex = FindLayer("Country");
	IFeatureLayer pFL = axMapControl1.Map.get_Layer(LayerIndex) as IFeatureLayer;
	IFeatureClass pFC = pFL.FeatureClass;
	int index = pFC.FindField("CNTRY_NAME");
		
	IFeatureSelection pFS = pFL as IFeatureSelection;
	ISelectionSet pSS = pFS.SelectionSet;
	ICursor pCursor;
	pSS.Search(null, true,out pCursor);
	IFeatureCursor pFCur = pCursor as IFeatureCursor;
	IFeature pFea = pFCur.NextFeature();
	while (pFea != null)
	{
		MessageBox.Show("你选中的国家为：" + pFea.get_Value(index).ToString());
		
		pFea = pFCur.NextFeature();
	}
}


//SpatialFilter
private void button2_Click(object sender, EventArgs e)
{
	int LayerIndex = FindLayer("Cities");
	
	IFeatureLayer pFL = axMapControl1.Map.get_Layer(LayerIndex) as IFeatureLayer;
	IFeatureClass pFC = pFL.FeatureClass;
		
	//☆获取选中要素的属性（IMap.FeatureSelection方法获取Feature的属性信息）
	ISelection pSelection = axMapControl1.Map.FeatureSelection; //获取选择集
	IEnumFeatureSetup pEnumFS = pSelection as IEnumFeatureSetup;    //打开属性标签
	pEnumFS.AllFields = true; //设置所有字段显示
	IEnumFeature pEnumF = pSelection as IEnumFeature; //读取属性
	IFeature pFea = pEnumF.Next();
	
	if (pFea != null)
	{
		ISpatialFilter pSF = new SpatialFilterClass();
		pSF.Geometry = pFea.Shape;
		pSF.SpatialRel = esriSpatialRelEnum.esriSpatialRelContains; //面中包含的点
		pSF.WhereClause = "Population > 2000000";
	
		int City_Count = pFC.FeatureCount(pSF);
		
		/* (优化代码，统计个数可以直接用上面的pFC.FeatureCount)
		IFeatureCursor pFCur = pFC.Search(pSF, true); //建立游标
		IFeature pFea1 = pFCur.NextFeature();
					
		int City_Count = 0;
		while (pFea1 != null)
		{
			City_Count++;
			
			pFea1 = pFCur.NextFeature();
		}
		*/
		MessageBox.Show(City_Count.ToString() + " cities with population > 2000000");
	}
	else
	{
		MessageBox.Show("未选中Country！");
	}
}

3.选中满足条件的Cities

private void button3_Click(object sender, EventArgs e)
{
	int LayerIndex = FindLayer("Cities");
	
	IFeatureLayer pFL = axMapControl1.Map.get_Layer(LayerIndex) as IFeatureLayer;
	IFeatureClass pFC = pFL.FeatureClass;
	
	----------------选中Country中的Cities-----------------/
	//☆获取选中要素的属性（IMap.FeatureSelection方法获取Feature的属性信息）
	ISelection pSelection = axMapControl1.Map.FeatureSelection; //获取选择集
	IEnumFeatureSetup pEnumFS = pSelection as IEnumFeatureSetup;    //打开属性标签
	pEnumFS.AllFields = true; //设置所有字段显示
	IEnumFeature pEnumF = pSelection as IEnumFeature; //读取属性 
	IFeature pFea = pEnumF.Next();
	
	if  (pFea != null)
	{
		axMapControl1.Map.ClearSelection(); //清空选择
		
		IFeatureSelection pFS = pFL as IFeatureSelection;		
		ISpatialFilter pSF = new SpatialFilterClass();
		pSF.Geometry = pFea.Shape;
		pSF.SpatialRel = esriSpatialRelEnum.esriSpatialRelContains;//面包含点
		pSF.WhereClause = "Population > 2000000";
		
		pFS.SelectFeatures(pSF, esriSelectionResultEnum.esriSelectionResultNew, false);
		
		/* （优化代码，可以用上面的IFeatureSelectionn的SelectFeatures 替代 axMapControl1.Map.SelectFeaure）
		IFeatureCursor pFCur = pFC.Search(pSF,true);
		IFeature pFea1 = pFCur.NextFeature();
				
		while (pFea1 != null)
		{
			axMapControl1.Map.SelectFeature(pFL, pFea1);
			
			pFea1 = pFCur.NextFeature();
		}
		*/
	}
	axMapControl1.ActiveView.Refresh();
}