Limbo Packages » Skybrud.Essentials.Maps » Documentation » GeoJSON » Features

Features

A feature is typically the root object, and can be either of the two following types:

Feature

A GeoJSON Feature consists of a type property and a geometry property, but may also specify an optional properties property wil an object of custom properties.

Being a feature, the type property should always be Feature (the GeoJsonFeature class within this package will handle that for you). The feature property can be any of the geometry types supported by GeoJSON.

A quick example of a feature is as shown below. The feature contains the geometry for a point. Notice that GeoJSON specifies coordinates as x and y, which corresponds with longitude and latitude (in that order), whereas one normally writes coordinates with latitude first, then longitude. The properties property is just a collection of custom properties, so it this case we can use properties.name to associate a name with the feature/point.

{
  "type": "Feature",
  "geometry": {
    "type": "Point",
    "coordinates": [9.536067, 55.708116]
  },
  "properties": {
    "name": "Skybrud.dk HQ"
  }
}

To generate a JSON string like in the example above, you can use the GeoJsonFeature, GeoJsonPoint and GeoJsonProperties classes from this package:

// Initialize a new feature for a point
GeoJsonFeature feature = new GeoJsonFeature {
    Geometry = new GeoJsonPoint(9.536067, 55.708116),
    Properties = new GeoJsonProperties {
        Name = "Skybrud.dk HQ"
    }
};

// Convert the feature to a JSON string
string json = feature.ToJson(Formatting.Indented);

Feature Collection

Where a Feature specifies a geometry on the map, a FeatureCollection on the other hand can contain an array of Feature objects.

For a feature collection containing the feature from before, the JSON wil now look as:

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "geometry": {
        "type": "Point",
        "coordinates": [9.536067, 55.708116]
      },
      "properties": {
        "name": "Skybrud.dk HQ"
      }
    }
  ]
}

And the code for generating that JSON:

// Initialize a new feature collection
GeoJsonFeatureCollection collection = new GeoJsonFeatureCollection();

// Add a new feature to the collection
collection.Features.Add(new GeoJsonFeature {
    Geometry = new GeoJsonPoint(9.536067, 55.708116),
    Properties = new GeoJsonProperties {
        Name = "Skybrud.dk HQ"
    }
});

// Convert the feature to a JSON string
string json = collection.ToJson(Formatting.Indented);

Properties

The properties object is a collection of child properties of various types supported by JSON - it may be simple types such as numbers, booleans and strings, but more comples types such as arrays and objects are allowed as well.

With this package, the properties object is represented by the GeoJsonProperties class. It wraps around a standard instance of Dictionary<string, object>, so you may add a key with a value of any type to it, and JSON.net will do the rest when serializing to JSON:

// Initialize a new properties dictionary
GeoJsonProperties properties = new GeoJsonProperties();

// Set the "name" and "address" properties
properties["name"] = "Skybrud.dk HQ";
properties["address"] = new {
    street = "Dæmningen 36",
    postal = "7100",
    city = "Vejle"
};

GeoJSON does not specify the format of any child properties of the properties property, so this is fully up to you. There does however seems to be some somewhat standardized properties, and as such the GeoJsonProperties class contains the following properties:

  • Name (serialized as name)
  • Description (serialized as description)
  • Fill (serialized as fill)
  • FillOpacity (serialized as fill-opacity)
  • MarkerColor (serialized as marker-color)
  • MarkerSymbol (serialized as marker-symbol)
  • Stroke (serialized as stroke)
  • StrokeWidth (serialized as stroke-width)
  • StrokeOpacity (serialized as stroke-opacity)
  • MarkerSize (serialized as marker-size)

Most of these are used for the visual presentation of the geometry of a Feature.

According to the GeoJSON specification, only a Feature may specify the properties property. But most GeoJSON parses will simply ignore any additional properties, so it should be somewhat safe to specify the properties property on a FeatureCollection as well.

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Geometry