Find features in a feature table which match an SQL query.
Use case
Query expressions can be used in ArcGIS to select a subset of features from a feature table. This is most useful in large or complicated data sets. A possible use case might be on a feature table marking the location of street furniture through a city. A user may wish to query by a TYPE column to return "benches". In this sample, we query a U.S. state by STATE_NAME from a feature table containing all U.S. states.
How to use the sample
Input the name of a U.S. state into the text field. When you tap the button, a query is performed and the matching features are highlighted or an error is returned.
How it works
- Create a
ServiceFeatureTable
using the URL of a feature service. - Create a
QueryParameters
with a where clause specified using theWhereClause
property. - Perform the query using
QueryFeaturesAsync(query)
on the service feature table. - When complete, the query will return a
FeatureQueryResult
which can be iterated over to get the matching features.
Relevant API
- FeatureLayer
- FeatureQueryResult
- QueryParameters
- ServiceFeatureTable
About the data
This sample uses U.S. State polygon features from the USA 2016 Daytime Population feature service.
Tags
query, search
Sample Code
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage x:Class="ArcGISRuntime.Samples.FeatureLayerQuery.FeatureLayerQuery"
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:esriUI="clr-namespace:Esri.ArcGISRuntime.Xamarin.Forms;assembly=Esri.ArcGISRuntime.Xamarin.Forms">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="auto" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<StackLayout Orientation="Vertical">
<Entry x:Name="queryEntry" Text="New York" />
<Button Clicked="OnQueryClicked" Text="Query" />
</StackLayout>
<esriUI:MapView x:Name="myMapView" Grid.Row="1" />
</Grid>
</ContentPage>