网页的本质就是超级文本标记语言，通过结合使用其他的Web技术（如：脚本语言、公共网关接口、组件等），可以创造出功能强大的网页。因而，超级文本标记语言是万维网（Web）编程的基础，也就是说万维网是建立在超文本基础之上的。超级文本标记语言之所以称为超文本标记语言，是因为文本中包含了所谓“超级链接”点。
arcgis 执行查询任务（QueryTask）还有ExecuteAsync？需进一步了解
url = string.Format("http://{0}/arcgis2/rest/services/baidu/MapServer/{1}", ip, layerID);
QueryTask queryTask = new QueryTask(url);
queryTask.ExecuteCompleted += new EventHandler<QueryEventArgs>(queryTask_ExecuteCompleted);
queryTask.Failed += new EventHandler<TaskFailedEventArgs>(queryTask_Failed);
ESRI.ArcGIS.Client.Tasks.Query query = new ESRI.ArcGIS.Client.Tasks.Query();
query.OutFields.Add("*");
query.ReturnGeometry = true;
query.Where = string.Format("FID={0}", QueryText);
queryTask.ExecuteAsync(query);
private void queryTask_Failed(object sender, TaskFailedEventArgs e)
{
MessageBox.Show("Query failed: " + e.Error);
}
private void queryTask_ExecuteCompleted(object sender, QueryEventArgs e)
{
FeatureSet featureSet = e.FeatureSet;
if (featureSet != null && featureSet.Features.Count > 0)
{
Graphic selectedFeature = featureSet.Features[0];
// 放大到选择的要素
ESRI.ArcGIS.Client.Geometry.Envelope selectedFeatureExtent = selectedFeature.Geometry.Extent;
double expandPercentage = 30;
double widthExpand = 2000 * (expandPercentage / 100);
double heightExpand = 2000 * (expandPercentage / 100);
ESRI.ArcGIS.Client.Geometry.Envelope displayExtent = new ESRI.ArcGIS.Client.Geometry.Envelope(
selectedFeatureExtent.XMin - (widthExpand / 2),
selectedFeatureExtent.YMin - (heightExpand / 2),
selectedFeatureExtent.XMax + (widthExpand / 2),
selectedFeatureExtent.YMax + (heightExpand / 2));
myMap.ZoomDuration = new TimeSpan(0, 0, 2);
myMap.ZoomTo(displayExtent);
}
}