Loading Geopackage PolyLines into ThinkGeo InMemoryFeatureLayer for use with ThinkGeo.UI.WinForms.MapView in C#

Question

I am trying to find most efective way to load Geopackage polyLines geometries into ThinkGeo InMemoryFeatureLayer. I have a working solution utilizing the Microsoft Sqlite and NetTopologySuite suite / nuggets. I'm looking for solution which will directly load the geopackage database into the InMemoryFeatureLayer.

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using Microsoft.Data.Sqlite;
using NetTopologySuite.Geometries;
using NetTopologySuite.IO;
using ThinkGeo.Core;
using ThinkGeo.UI.WinForms;

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GeoPackageGeoReader gpkgReader = new GeoPackageGeoReader(); // for reading geopackage blob
WKBWriter wkbWriter = new WKBWriter();                      // for converting the GeoPackageGeoReader to standard wkb  

using (SqliteConnection SQLiteConnection = new SqliteConnection(@"Data Source=:memory:"))
{
    using (SqliteCommand SQLiteCommand = new SqliteCommand())
    {
        SQLiteCommand.CommandText =
            $@"

            ATTACH 'c:\temp\lines.gpkg' as lines_;
            CREATE TEMP TABLE IF NOT EXISTS lines
            AS SELECT * FROM lines_.lines;
            DETACH lines_;

            SELECT
                fid,
                _ogr_geometry_,
                street
            FROM lines;

            ";

        SQLiteCommand.Connection = SQLiteConnection;
        SQLiteConnection.Open();

        using (SqliteDataReader SQLiteDataReader = SQLiteCommand.ExecuteReader())
        {
            while (SQLiteDataReader.Read())
            {
                string id = SQLiteDataReader["fid"].ToString();
                byte[] geomData = (byte[])SQLiteDataReader.GetValue("_ogr_geometry_");

                Geometry geometry = gpkgReader.Read(geomData);      // get the geometry from the GeoPackage blob
                byte[] standardWkb = wkbWriter.Write(geometry);     // convert the gpkg blob to standard WKB

                Feature polyLineFeature = new Feature(standardWkb, id);
                polyLineFeature.Id = id;

                for (int i = 0; i < SQLiteDataReader.FieldCount; i++)
                {
                    string columnName = SQLiteDataReader.GetName(i);
                    object value = SQLiteDataReader.GetValue(i);

                    string valueAsString = value switch
                    {
                        null or DBNull => string.Empty, // handling null and DBNull values
                        string str => str,              // use it as is
                        _ => value.ToString()           // default - convert to string
                    };

                    polyLineFeature.ColumnValues.Add(columnName, valueAsString); // adding columns to feature
                }
                InMemoryFeatureLayer.InternalFeatures.Add(polyLineFeature); // adding row to InMemoryFeatureLayer
            }
            InMemoryFeatureLayer.BuildIndex();
        }
    }
}

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Answer 1

ThinkGeo recently formalized GeoPackage support using the GdalFeatureLayer class.

Try the following code:

        // Create a new layerOverlay to hold the gdalFeatureLayers
        var layerOverlay = new LayerOverlay();
        var projectionConverter = new ProjectionConverter(26910, 3857);
        projectionConverter.Open();

        // Create the gdalFeatureLayers
        var gdalFeatureLayer = new GdalFeatureLayer(@"./Data/GeoPackage/mora_surficial_geology.gpkg");
        gdalFeatureLayer.FeatureSource.ProjectionConverter = projectionConverter;
        gdalFeatureLayer.ZoomLevelSet.ZoomLevel01.DefaultPointStyle = PointStyle.CreateSimplePointStyle(PointSymbolType.Circle,GeoColors.LightRed,4);
        gdalFeatureLayer.ZoomLevelSet.ZoomLevel01.DefaultLineStyle = LineStyle.CreateSimpleLineStyle(GeoColor.FromArgb(128,GeoColors.LightSteelBlue), 2F, GeoColors.Black, 2F, false);
        gdalFeatureLayer.ZoomLevelSet.ZoomLevel01.DefaultAreaStyle = AreaStyle.CreateSimpleAreaStyle(GeoColor.FromArgb(64,GeoColors.LightGreen), GeoColors.Black, 1);
        gdalFeatureLayer.ZoomLevelSet.ZoomLevel01.ApplyUntilZoomLevel = ApplyUntilZoomLevel.Level20;
        layerOverlay.Layers.Add(gdalFeatureLayer);