GIS一般都具有属性查询和空间查询的功能，今天又抽空用sharpMap在之一的基础上写了个基本属性信息查询的实例，实现的功能就是通过选定图层，输入查询条件，查询所选图层中满足条件的要素，并显示基本信息。以下是效果图：
以下是源代码
///////////////////////////////////////
按钮点击事件
protected void btQuery_Click(object sender, EventArgs e) //属性查询
{
if (this.txtQuery.Text.Trim() == "") return;
//获取图层名
string lyrName = this.DDLayers.Items[this.DDLayers.SelectedIndex].Value+".shp";
if (szmap == null) return;
//获取图层
SharpMap.Layers.VectorLayer lyr = szmap.GetLayerByName(lyrName) as SharpMap.Layers.VectorLayer ;
if (lyr == null) return;
if (!lyr.DataSource.IsOpen) lyr.DataSource.Open();
//获取图层的所有元素
//法一：通过获取地图全图范围内的要素，也就是所有的要素，这种方法需要执行几何要素的相交判断
//SharpMap.Data.FeatureDataSet ds = new SharpMap.Data.FeatureDataSet();
//lyr.DataSource.ExecuteIntersectionQuery(lyr.Envelope, ds);
//法二：为shapefile类添加一个方法GetFeaturesDataSet()，直接获取所有的要素，不需要进行几何要素的相交判断
SharpMap.Data.Providers.ShapeFile shapefile = (SharpMap.Data.Providers.ShapeFile)lyr.DataSource;
SharpMap.Data.FeatureDataSet ds = shapefile.GetFeaturesDataSet();
lyr.DataSource.Close();
if (ds == null) return;
System.Data.DataTable dt=new DataTable();
System.Data.DataColumn dc=new DataColumn("名字",typeof(System.String));
dt.Columns.Add(dc);
foreach (SharpMap.Data.FeatureDataRow row in ds.Tables[0])
{
if (row["NAME"].ToString().Contains(this.txtQuery.Text.Trim()))
{
System.Data.DataRow r = dt.NewRow();
r[0] = row["NAME"].ToString();
dt.Rows.Add(r);
}
}
this.gvResults.DataSource = dt;
this.gvResults.DataBind();
//重新生成地图
this.GenerateMap();
}
对于法二，我在sharpMap的ShapeFile类中添加了一个方法以获取全部要素
public FeatureDataSet GetFeaturesDataSet()
{
FeatureDataSet featDataSet = new FeatureDataSet();
FeatureDataTable featDataTable = null;
if(!this.IsOpen )
throw (new ApplicationException("An attempt was made to read from a closed datasource"));
if(this.dbaseFile ==null)
throw (new ApplicationException("An attempt was made to read DBase data from a shapefile without a valid .DBF file"));
//获取feature数量
int featCount = this.GetFeatureCount();
featDataTable = this.dbaseFile.NewTable;
//获取feature
for (uint i = 0; i < featCount; i++)
{
FeatureDataRow r= this.GetFeature(i,featDataTable);
featDataTable.AddRow(r);
}
featDataSet.Tables.Add(featDataTable);
return featDataSet ;
}
实例均是在上一个学习笔记的基础上做的，这里的属性查询功能比较简单，主要提供查询的原理，如果有必要，可以通过需要进行相应的改写。
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