Npgsql: Explore communicating and marshalling GeoJSON types

Currently, this has to be conducted "manually".

by-language/csharp-npgsql/DemoProgram.cs

@@ -17,12 +17,8 @@ await Parser.Default.ParseArguments<Options>(args)
                 {
                     var connString = $"Host={options.Host};Port={options.Port};SSL Mode={options.SslMode};" +
                                      $"Username={options.Username};Password={options.Password};Database={options.Database}";
-                    Console.WriteLine($"Connecting to {connString}\n");
 
-                    var dataSourceBuilder = new NpgsqlDataSourceBuilder(connString);
-                    dataSourceBuilder.EnableDynamicJson();
-                    await using var dataSource = dataSourceBuilder.Build();
-                    await using var conn = dataSource.OpenConnection();
+                    await using var conn = GetConnection(connString);
 
                     await DatabaseWorkloads.SystemQueryExample(conn);
                     await DatabaseWorkloads.BasicConversationExample(conn);
@@ -34,11 +30,34 @@ await Parser.Default.ParseArguments<Options>(args)
                     // await dwt.ArrayJsonDocumentExample();
                     await dwt.ObjectPocoExample();
                     await dwt.ArrayPocoExample();
+                    await dwt.GeoJsonTypesExample();
                     conn.Close();
                 });
 
         }
 
+        public static NpgsqlConnection GetConnection(string connString)
+        {
+            Console.WriteLine($"Connecting to database: {connString}\n");
+
+            // Enable JSON POCO mapping and PostGIS/GeoJSON Type Plugin.
+            // https://www.npgsql.org/doc/types/json.html
+            // https://www.npgsql.org/doc/types/geojson.html
+            var dataSourceBuilder = new NpgsqlDataSourceBuilder(connString);
+
+            // Enable JSON POCO mapping Plugin.
+            // https://www.npgsql.org/doc/types/json.html
+            dataSourceBuilder.EnableDynamicJson();
+
+            // Enable PostGIS/GeoJSON Type Plugin.
+            // https://www.npgsql.org/doc/types/geojson.html
+            // dataSourceBuilder.UseGeoJson();
+
+            var dataSource = dataSourceBuilder.Build();
+            var conn = dataSource.OpenConnection();
+            return conn;
+        }
+
         public class Options
         {
             [Option('h', "host", Required = false, HelpText = "Host name to connect to", Default = "localhost")]

by-language/csharp-npgsql/DemoTypes.cs

@@ -4,6 +4,7 @@
 using System.Data;
 using System.Text.Json;
 using System.Threading.Tasks;
+using GeoJSON.Net.Geometry;
 using Newtonsoft.Json;
 using Npgsql;
 using NpgsqlTypes;
@@ -351,6 +352,102 @@ public async Task<List<BasicPoco>> ArrayPocoExample()
             }
         }
 
+        public async Task InsertGeoJsonTyped()
+        {
+            /***
+             * Verify Npgsql PostGIS/GeoJSON Type Plugin with CrateDB.
+             * https://www.npgsql.org/doc/types/geojson.html
+             *
+             * TODO: Does not work yet, because CrateDB communicates GEO_SHAPE as string?
+             *       The error message is:
+             *
+             *       System.NotSupportedException : The NpgsqlDbType 'Geometry' isn't present in your
+             *       database. You may need to install an extension or upgrade to a newer version.
+             */
+            Console.WriteLine("Running InsertGeo");
+
+            // Insert single data point.
+            await using (var cmd = new NpgsqlCommand("""
+            INSERT INTO testdrive.example (
+                "geoshape"
+            ) VALUES (
+                @geoshape
+            );
+            """, conn))
+            {
+                var point = new Point(new Position(85.43, 66.23));
+                cmd.Parameters.AddWithValue("geoshape", NpgsqlDbType.Geometry, point);
+                cmd.ExecuteNonQuery();
+            }
+
+            // Flush data.
+            await RefreshTable();
+        }
+
+        public async Task InsertGeoJsonString()
+        {
+            /***
+             * Communicate GeoJSON types as strings, marshall from/to GeoJSON types manually.
+             */
+            Console.WriteLine("Running InsertGeoRaw");
+
+            // Insert single data point.
+            await using (var cmd = new NpgsqlCommand("""
+            INSERT INTO testdrive.example (
+                "geoshape"
+            ) VALUES (
+                @geoshape
+            );
+            """, conn))
+            {
+                var point = new Point(new Position(85.43, 66.23));
+                var poly = new Polygon([
+                    new LineString([
+                        new Position(longitude: 5.0, latitude: 5.0),
+                        new Position(longitude: 5.0, latitude: 10.0),
+                        new Position(longitude: 10.0, latitude: 10.0),
+                        new Position(longitude: 10.0, latitude: 5.0),
+                        new Position(longitude: 5.0, latitude: 5.0),
+                    ])
+                ]);
+                // TODO: Can GEO_SHAPE types be directly marshalled to a .NET GeoJSON type?
+                //       Currently, `InsertGeoJsonTyped` does not work yet.
+                cmd.Parameters.AddWithValue("geoshape", NpgsqlDbType.Json, JsonConvert.SerializeObject(point));
+                cmd.ExecuteNonQuery();
+
+                cmd.Parameters.Clear();
+
+                cmd.Parameters.AddWithValue("geoshape", NpgsqlDbType.Json, JsonConvert.SerializeObject(poly));
+                cmd.ExecuteNonQuery();
+            }
+
+            // Flush data.
+            await RefreshTable();
+
+        }
+
+        public async Task<Point> GeoJsonTypesExample()
+        {
+            Console.WriteLine("Running GeoJsonTypesExample");
+
+            // Provision data.
+            await CreateTable();
+            // await InsertGeoJsonTyped();
+            await InsertGeoJsonString();
+
+            // Query back data.
+            await using (var cmd = new NpgsqlCommand("SELECT * FROM testdrive.example", conn))
+            await using (var reader = cmd.ExecuteReader())
+            {
+                reader.Read();
+                // TODO: Can GEO_SHAPE types be directly marshalled to a .NET GeoJSON type?
+                //       Currently, `InsertGeoJsonTyped` does not work yet.
+                var obj = reader.GetFieldValue<JsonDocument>("geoshape");
+                var geoJsonObject = JsonConvert.DeserializeObject<Point>(obj.RootElement.ToString());
+                return (Point) geoJsonObject;
+            }
+        }
+
     }
 
 }

by-language/csharp-npgsql/demo.csproj

@@ -10,6 +10,7 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="GeoJSON.Net" Version="1.4.1" />
     <PackageReference Include="Npgsql" Version="9.0.2" />
     <PackageReference Include="CommandLineParser" Version="2.9.1" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />

by-language/csharp-npgsql/tests/DemoProgramTest.cs

@@ -4,6 +4,7 @@
 using System.Linq;
 using System.Text.Json;
 using System.Threading.Tasks;
+using GeoJSON.Net.Geometry;
 using Npgsql;
 using NpgsqlTypes;
 using Xunit;
@@ -22,12 +23,7 @@ public DatabaseFixture()
             {
                 CRATEDB_DSN = $"Host=localhost;Port=5432;Username=crate;Password=;Database=testdrive";
             }
-            Console.WriteLine($"Connecting to {CRATEDB_DSN}\n");
-
-            var dataSourceBuilder = new NpgsqlDataSourceBuilder(CRATEDB_DSN);
-            dataSourceBuilder.EnableDynamicJson();
-            using var dataSource = dataSourceBuilder.Build();
-            Db = dataSource.OpenConnection();
+            Db = DemoProgram.GetConnection(CRATEDB_DSN);
         }
 
         public void Dispose()
@@ -216,5 +212,21 @@ public async Task TestArrayPocoExample()
 
         }
 
+        [Fact]
+        public async Task TestGeoJsonTypesExample()
+        {
+            var conn = fixture.Db;
+
+            // Provision data.
+            var task = new DatabaseWorkloadsTypes(conn).GeoJsonTypesExample();
+            var point = await task.WaitAsync(TimeSpan.FromSeconds(0.5));
+
+            // Validate the outcome.
+            var coords = new Point(new Position(85.43, 66.23)).Coordinates;
+            Assert.Equal(coords.Latitude, point.Coordinates.Latitude);
+            Assert.Equal(coords.Longitude, point.Coordinates.Longitude);
+
+        }
+
     }
 }