Zoom-in to feature in ArcGIS Engine using ArcGIS Server and REST

The first blog post on how to use ArcGIS Server from ArcGIS Engine. This post show how to zoom in on a feature using a custom query.

I start by creating JSON query:

 Private Sub TestREST2ToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TestREST2ToolStripMenuItem.Click
     Dim state As String = "Alaska"
     'Skapar fråga för REST:
     Dim requestUri As String = "http://server.arcgisonline.com/ArcGIS/rest/services/Demographics/USA_Median_Household_Income/MapServer/4/query"
     Dim data As New StringBuilder()
     data.AppendFormat("?f={0}", "json")
     'case sensitive
     data.AppendFormat("&Where=Name%3D'" & state & "'")
     data.AppendFormat("&returnGeometry=true")
     data.AppendFormat("&returnIdsOnly=false")
     data.AppendFormat("&outFields=*")
     ZoomTo(requestUri, data.ToString())
   End Sub 

Check out the service http://server.arcgisonline.com/ArcGIS/rest/services/Demographics/USA_Median_Household_Income/MapServer/4/query to find out what questions you can ask.

The ZoomTo method looks like this and loops through the result for the features returned and zoom in to the extent of the polygon returned:

 Sub ZoomTo(ByVal requestUri As String, ByVal data As String)
     'Ställer REST frågan:
     Dim request As HttpWebRequest = TryCast(WebRequest.Create(requestUri & data), HttpWebRequest)
     'Hanterar resultat
     Using response As HttpWebResponse = TryCast(request.GetResponse(), HttpWebResponse)
       Dim reader As New StreamReader(response.GetResponseStream())
       Dim responseString As String = reader.ReadToEnd()
       Dim jss As New System.Web.Script.Serialization.JavaScriptSerializer()
       jss.MaxJsonLength = 10000000
       'Skulle kunna köra med datakontrakt, men då måste man skapa objektstrukturen.
       'DataContractJsonSerializer ser = new DataContractJsonSerializer(typeof(object))
       'Parsar resultatet för att skapa upp polygon.
       Dim results As IDictionary(Of String, Object) = TryCast(jss.DeserializeObject(responseString), IDictionary(Of String, Object))
       If results IsNot Nothing AndAlso results.ContainsKey("features") Then
         Dim features As IEnumerable(Of Object) = TryCast(results("features"), IEnumerable(Of Object))
         For Each feature As IDictionary(Of String, Object) In features
           Dim geometries As IDictionary(Of String, Object) = TryCast(feature("geometry"), IDictionary(Of String, Object))
           Dim polygon As Polygon = New Polygon()
           Dim rings As IEnumerable(Of Object) = TryCast(geometries("rings"), IEnumerable(Of Object))
           Dim i As Integer = rings.Count()
           For Each ring As IEnumerable(Of Object) In rings
             Dim pointCol As IPointCollection = New Ring()
             For Each vertex As IEnumerable(Of Object) In ring
               Dim point As IPoint = New Point()
               point.X = Convert.ToDouble(vertex.ElementAt(0))
               point.Y = Convert.ToDouble(vertex.ElementAt(1))
               pointCol.AddPoint(point)
             Next
             polygon.AddPointCollection(pointCol)
           Next
           'Sätter om extent via polygonens
           Dim control As AxMapControl = axMapControl1
           control.ActiveView.Extent = TryCast(polygon, IPolygon).Envelope
           control.ActiveView.PartialRefresh(esriViewDrawPhase.esriViewAll, Nothing, Nothing)
           'GetLegend()
           'Dim attributes As IDictionary(Of String, Object) = TryCast(feature("attributes"), IDictionary(Of String, Object))
         Next
       End If
     End Using  
   End Sub  

I'm making a lot of assumptions here, that the result is a polygon, that there is only one polygon returned. But it shows the concept of getting features using REST.



The test application shows US when I start:



And zoom in on Alaska when I run the test method:


I have not done anything to boost the performance, so it feels very slow.