Write or Access GIS Features from TopoJSON format in C#

Working with TopoJSON Format

Access features in TopoJSON

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
string sampleTopoJsonPath = RunExamples.GetDataDir() + "sample.topojson";
StringBuilder builder = new StringBuilder();
using (VectorLayer layer = VectorLayer.Open(sampleTopoJsonPath, Drivers.TopoJson))
{
    foreach (Feature feature in layer)
    {
        // get id property
        int id = feature.GetValue<int>("id");

        // get name of the object that contains this feature
        string objectName = feature.GetValue<string>("topojson_object_name");

        // get name attribute property, located inside 'properties' object
        string name = feature.GetValue<string>("name");

        // get geometry of the feature.
        string geometry = feature.Geometry.AsText();

        builder.AppendFormat("Feature with ID {0}:\n", id);
        builder.AppendFormat("Object Name = {0}\n", objectName);
        builder.AppendFormat("Name        = {0}\n", name);
        builder.AppendFormat("Geometry    = {0}\n", geometry);
    }
}

Console.WriteLine("Output:");
Console.WriteLine(builder.ToString());

// Output:
// Feature with ID 0:
// Object Name = named_object_1
// Name        = point_feature
// Geometry    = POINT (102 0.5)
// Feature with ID 1:
// Object Name = named_object_1
// Name        = line_feature
// Geometry    = LINESTRING (102 0, 103 1, 104 0, 105 1)
// Feature with ID 2:
// Object Name = named_object_2
// Name        = polygon_feature
// Geometry    = POLYGON ((100 0, 100 1, 101 1, 101 0, 100 0))

Write features to TopoJSON

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
var outputPath = RunExamples.GetDataDir() + "sample_out.topojson";

using (VectorLayer layer = VectorLayer.Create(outputPath, Drivers.TopoJson))
{
    // add attributes that we are going to set
    layer.Attributes.Add(new FeatureAttribute("name", AttributeDataType.String));
    layer.Attributes.Add(new FeatureAttribute("measurement", AttributeDataType.Double));
    layer.Attributes.Add(new FeatureAttribute("id", AttributeDataType.Integer));

    var feature0 = layer.ConstructFeature();
    feature0.SetValue("name", "name_0");
    feature0.SetValue("measurement", 1.03);
    feature0.SetValue("id", 0);
    feature0.Geometry = new Point(1.3, 2.3);
    layer.Add(feature0);

    var feature1 = layer.ConstructFeature();
    feature1.SetValue("name", "name_1");
    feature1.SetValue("measurement", 10.03);
    feature1.SetValue("id", 1);
    feature1.Geometry = new Point(241.32, 23.2);
    layer.Add(feature1);
}