NetTopologySuite

Weasel.Postgresql includes built-in support for spatial types via NetTopologySuite and the PostGIS extension.

Prerequisites

Ensure PostGIS is installed in your database and the Npgsql NetTopologySuite plugin is configured:

dotnet add package Npgsql.NetTopologySuite
dotnet add package Weasel.Postgresql

Enable the PostGIS extension in your database schema:

yield return new Extension("postgis");

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NpgsqlDataSource Configuration

Register the NetTopologySuite type mappings when building your data source:

var builder = new NpgsqlDataSourceBuilder("Host=localhost;Database=myapp;");
builder.UseNetTopologySuite();
await using var dataSource = builder.Build();

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Type Mappings

Weasel automatically maps NetTopologySuite.Geometries.Geometry (and its subclasses) to the PostgreSQL geometry type. This mapping is included in the default NpgsqlTypeMapper.

.NET Type	PostgreSQL Type
Geometry	geometry
Point	geometry
LineString	geometry
Polygon	geometry
MultiPoint	geometry
MultiLineString	geometry
MultiPolygon	geometry
GeometryCollection	geometry

Using Spatial Columns

Define geometry columns on your tables:

var table = new Table("locations");
table.AddColumn<int>("id").AsPrimaryKey();
table.AddColumn<string>("name").NotNull();
table.AddColumn<Geometry>("geom");

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This generates a column of type geometry. For more specific PostGIS types, use the string overload:

var table = new Table("locations");
table.AddColumn("geom", "geometry(Point, 4326)");

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Spatial Indexes

Create a GiST index for spatial queries:

var table = new Table("locations");

var index = new IndexDefinition("idx_locations_geom")
{
    Method = IndexMethod.gist
};
index.Columns = new[] { "geom" };
table.Indexes.Add(index);

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This generates:

CREATE INDEX idx_locations_geom ON public.locations USING gist (geom);