Method GetGeoJSON

Namespace

YndigoBlue.Velocity.Engine

Assembly

YndigoBlue.Velocity.dll

GetGeoJSON(string, string)

Converts query results containing geospatial data to GeoJSON format.

public string GetGeoJSON(string geospatialColumnName, string idPropertyName = "id")

Parameters

geospatialColumnName string

The name of the column containing geometry or geography data.

idPropertyName string

The attribute name promoted from GeoJSON "properties" to the Feature's top-level "id" member (the idiomatic GeoJSON convention for a row's identifier, recognized by tools such as Mapbox GL and Leaflet). Pass null or an empty string to disable promotion and leave it as a regular property.

Returns

string

A GeoJSON FeatureCollection string containing all results.

Examples

var conn = new PostgreSqlDatasourceConnection
{
    Hostname = "localhost",
    Database = "gis_data",
    Username = "user",
    Password = "password"
};

using (var manager = new Manager(conn))
{
    var schema = manager.LoadSchema("public");
    var locationsTable = schema["locations"];

    var query = new Query()
        .Select([locationsTable["id"], locationsTable["name"], locationsTable["geom"]])
        .From(locationsTable);

    using (ResultReader reader = manager.Search(query))
    {
        // Convert results to GeoJSON — the "id" column is promoted to each Feature's top-level "id"
        string geoJson = reader.GetGeoJSON("geom");
        File.WriteAllText("locations.geojson", geoJson);
    }
}

Remarks

Warning

GeoJSON export for geospatial data is not available in the Community Edition of Velocity. It requires the Full Edition.

This overload materializes every feature in memory before returning the completed string. For large result sets, prefer the GetGeoJSON(Stream, string, string) overload, which writes each feature to the stream as it's read, holding only one row in memory at a time.

GetGeoJSON(Stream, string, string)

Converts query results containing geospatial data to GeoJSON format, writing each feature to stream as it's read rather than materializing the entire result set in memory first.

public void GetGeoJSON(Stream stream, string geospatialColumnName, string idPropertyName = "id")

Parameters

stream Stream

The stream to write the GeoJSON to. Not closed by this method.

geospatialColumnName string

The name of the column containing geometry or geography data.

idPropertyName string

The attribute name promoted from GeoJSON "properties" to the Feature's top-level "id" member. Pass null or an empty string to disable promotion and leave it as a regular property.

Examples

using (var manager = new Manager(conn))
using (ResultReader reader = manager.Search(query))
using (FileStream file = File.Create("locations.geojson"))
{
    // Only one row is held in memory at a time, regardless of result set size
    reader.GetGeoJSON(file, "geom");
}

Remarks

Warning

GeoJSON export for geospatial data is not available in the Community Edition of Velocity. It requires the Full Edition.