While there is no direct way to do it in the Silverlight API or in REST, it is possible even if the layer you're querying has more features than the max # Features set on the service. Starting in version 10 you can query with the option to just retreive the ObjectIDs of the features that match your query. Since you're not returning features this way, the maximum # of features limitation is bypassed. Below is some simple example XAML and C# code to do exactly this in a 2 step approach -1. Get all the object IDs from the layer. Can be done using a query that is true for all features such as query.where = "1=1"2. Pull the objectIDs out in chunks of 1000 (the default max # of features for a v10 Server) and run a query that'll actually get the attribute(s) you need back & create a list of unique values from it.I wrote this up today as it's something I've been needing to do for a user but have been putting off and to hopefuly help gbushek and others. Also turned out to be a fun learning experience with some LINQ too..I tested this against a layer with 34,000 + features in it. Just getting the values from 1 field takes around 10 seconds to complete. The code below actually grabs 2 fields (county and state) from the data to build the list and takes closer to 15-20 seconds. Not the usual snappy response I'm used to with Silverlight but it does work.There are of course other options, depending on your data sources - WCF service calls or using SQL to LINQ and the Entity Framework come to mind. I'm also sure some of my code below code be more efficient but it's a start.... if anyone can speed it up, I'd love to hear about it.TerryXAML
<UserControl x:Class="ArcGISSilverlightSDK.RoutingDirections"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk"
xmlns:toolkit= "clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Toolkit"
xmlns:esri="http://schemas.esri.com/arcgis/client/2009">
<Grid x:Name="LayoutRoot" Background="White">
<Grid.Resources>
<esri:SimpleMarkerSymbol x:Key="FromSymbol" Size="15" Style="Circle" Color="#9900FF00" />
<esri:SimpleMarkerSymbol x:Key="ToSymbol" Size="15" Style="Circle" Color="#99FF0000" />
<esri:SimpleLineSymbol x:Key="RouteSymbol" Color="#990000FF" Width="5"/>
<esri:SimpleLineSymbol x:Key="SegmentSymbol" Color="#99FF0000" Width="8"/>
</Grid.Resources>
<Grid.RowDefinitions>
<!--<RowDefinition Height="30" />-->
<RowDefinition Height="75" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<toolkit:BusyIndicator x:Name="busy" IsBusy="False">
<StackPanel Orientation="Horizontal" >
<Button x:Name="btnTest" Content="pop cbox" Click="btnTest_Click" Width="75" Height="50" />
<ComboBox x:Name="cbxValues" Grid.Column="2" Grid.Row="1" Width="100" Height="50" />
</StackPanel>
</toolkit:BusyIndicator>
</Grid>
</UserControl>
C#
using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using ESRI.ArcGIS.Client;
using ESRI.ArcGIS.Client.Tasks;
namespace ArcGISSilverlightSDK
{
public partial class RoutingDirections : UserControl
{
public RoutingDirections()
{
InitializeComponent();
}
private int _featcount;
private int _featcomplete;
private List<string> uniquevalues;
private void btnTest_Click(object sender, RoutedEventArgs e)
{
System.Diagnostics.Debug.WriteLine("start " + System.DateTime.Now);
busy.IsBusy = true;
uniquevalues = new List<string>();
QueryTask qt = new QueryTask("http://myserver/ArcGIS/rest/services/MyService/MapServer/0");
qt.ExecuteCompleted += qt_ExecuteCompleted;
qt.Failed += qt_Failed;
Query qry = new Query();
qry.ReturnIdsOnly = true;
qry.Where = "1=1"; //get them all... ReturnIDsonly is not limited to the max #features set for a sevice
qt.ExecuteAsync(qry, qt.Url);
}
void qt_Failed(object sender, TaskFailedEventArgs e)
{
MessageBox.Show(e.Error.Message);
}
void qt_ExecuteCompleted(object sender, QueryEventArgs e)
{
_featcount += e.FeatureSet.ObjectIDs.Count();
if (_featcount == 0)
{
return;
}
int[] oids;
QueryTask qt = new QueryTask("http://myserver/ArcGIS/rest/services/MyService/MapServer/0");
Query qry = new Query();
//assuming max # features returned is stilll the v10.0 default of 1000 here....
for (int i = 0; i <= Math.Floor(_featcount / 1000); i++)
{
oids = e.FeatureSet.ObjectIDs.Skip(i * 1000).Take(1000).Select(x => int.Parse(x.ToString())).ToArray();
qt = new QueryTask("http://myserver/ArcGIS/rest/services/MyService/MapServer/0");
qt.ExecuteCompleted += fullqt_ExecuteCompleted;
qt.Failed += qt_Failed;
qry = new Query();
OutFields ofld = new OutFields();
ofld.Add("COUNTYNAME");
ofld.Add("STATE");
qry.OutFields = ofld;
qry.ObjectIDs = oids;
qt.ExecuteAsync(qry);
}
}
void fullqt_ExecuteCompleted(object sender, QueryEventArgs e)
{
foreach (Graphic g in e.FeatureSet)
{
_featcomplete += 1;
if (!uniquevalues.Contains(g.Attributes["COUNTYNAME"].ToString() + ", " + g.Attributes["STATE"].ToString()))
{
uniquevalues.Add(g.Attributes["COUNTYNAME"].ToString() + ", " + g.Attributes["STATE"].ToString());
}
}
if (_featcomplete == _featcount)
{
cbxValues.ItemsSource = uniquevalues;
System.Diagnostics.Debug.WriteLine("done " + System.DateTime.Now);
busy.IsBusy = false;
cbxValues.IsDropDownOpen = true;
}
}
}
}
