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ArcGIS Runtime SDK for .NET

Feature collection layer (query)

This code sample is available for these platforms:
View Sample on GitHub

Create a feature collection layer to show a query result from a service feature table.

Image of feature collection layer

Use case

Consider a national wireless telecommunications company who wants to improve connectivity within areas of poor coverage. Their cell towers, cell tower radii and state boundaries data are held within service feature tables, which can be queried for states that don't meet a certain threshold of coverage. The query result can be used to create and display a single feature collection layer for analysis of areas requiring improved coverage.

How to use the sample

When launched, this sample displays a map with point features as a feature collection layer. Pan and zoom to explore the map.

How it works

  1. Perform a query using the QueryFeaturesAsync() method on a ServiceFeatureTable.
  2. Instantiate a FeatureCollectionTable with the result of the query.
  3. Create a FeatureCollection and add the feature collection table to it.
  4. Create a FeatureCollectionLayer from the feature collection.
  5. Add the feature collection layer to the map's OperationalLayers list.

Relevant API

  • FeatureCollection
  • FeatureCollectionLayer
  • FeatureCollectionTable
  • FeatureLayer
  • FeatureQueryResult
  • FeatureTable
  • QueryParameters
  • ServiceFeatureTable

About the data

This application utilizes data from the wildfire feature service. It loads at full extent with features indicating wildfire response point features across the world.

Tags

layer, query, search, table

Sample Code

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage x:Class="ArcGISRuntime.Samples.FeatureCollectionLayerFromQuery.FeatureCollectionLayerFromQuery"
             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"
             xmlns:mapping="clr-namespace:Esri.ArcGISRuntime.Mapping;assembly=Esri.ArcGISRuntime">
  <Grid>
    <esriUI:MapView x:Name="MyMapView"/>
  </Grid>
</ContentPage>
// Copyright 2016 Esri.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License.
// You may obtain a copy of the License at: http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an 
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific 
// language governing permissions and limitations under the License.

using Esri.ArcGISRuntime.Data;
using Esri.ArcGISRuntime.Mapping;
using System;
using Xamarin.Forms;

namespace ArcGISRuntime.Samples.FeatureCollectionLayerFromQuery
{
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        name: "Feature collection layer (query)",
        category: "Layers",
        description: "Create a feature collection layer to show a query result from a service feature table.",
        instructions: "When launched, this sample displays a map with point features as a feature collection layer. Pan and zoom to explore the map.",
        tags: new[] { "layer", "query", "search", "table" })]
    public partial class FeatureCollectionLayerFromQuery : ContentPage
    {
        // Feature service URL to query for features
        private const string FeatureLayerUrl = "https://sampleserver6.arcgisonline.com/arcgis/rest/services/Wildfire/FeatureServer/0";

        public FeatureCollectionLayerFromQuery()
        {
            InitializeComponent();

            // call a function to initialize a map to display in the MyMapView control
            Initialize();
        }

        private void Initialize()
        {
            // Create a new map with the oceans basemap and add it to the map view
            Map myMap = new Map(Basemap.CreateOceans());
            MyMapView.Map = myMap;

            // Call a function that will create a new feature collection layer from a service query
            GetFeaturesFromQuery();
        }

        private async void GetFeaturesFromQuery()
        {
            try
            {
                // Create a service feature table to get features from
                ServiceFeatureTable featTable = new ServiceFeatureTable(new Uri(FeatureLayerUrl));

                // Create a query to get all features in the table
                QueryParameters queryParams = new QueryParameters
                {
                    WhereClause = "1=1"
                };

                // Query the table to get all features
                FeatureQueryResult featureResult = await featTable.QueryFeaturesAsync(queryParams);

                // Create a new feature collection table from the result features
                FeatureCollectionTable collectTable = new FeatureCollectionTable(featureResult);

                // Create a feature collection and add the table
                FeatureCollection featCollection = new FeatureCollection();
                featCollection.Tables.Add(collectTable);

                // Create a layer to display the feature collection, add it to the map's operational layers
                FeatureCollectionLayer featCollectionTable = new FeatureCollectionLayer(featCollection);
                MyMapView.Map.OperationalLayers.Add(featCollectionTable);
            }
            catch (Exception e)
            {
                await Application.Current.MainPage.DisplayAlert("Error", e.ToString(), "OK");
            }
        }
    }
}