EF Core NetTopologySuite Geometry becomes geography in SQL Server

Question

I have the follwoing ValueConverter class:

using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
using NetTopologySuite.Geometries;

public class GeometryConverter : ValueConverter<string, Geometry>
{
    public GeometryConverter(IWKTStringConverter converter)
        : base(
            wtkGeometry => converter.ConvertToGeometry(wtkGeometry),
            geometry => geometry.ToString())
    {
    }
}

And this is the builder for the entity:

var geomConverter = new Geo.GeometryConverter(new Geo.WKTStringConverter());
        
modelBuilder.Entity<GEOCatalog>(b => {
            b.ToTable("GEOCatalog").HasKey(m => m.Id);
            b.Property(m => m.Geom).HasConversion(geomConverter);
        });

When I now start my server, EF Core creates the tables, but the data type of the property Geom is geography instead of geometry which is not correct.

Even if I do not use a ValueConverter and create a model whose Geom property type is of type NetTopologySuite.Geometries.Geometry the result in SQL Server is the same.

Maybe anyone can help with that?

Answer 1

By default, spatial properties are mapped to geography columns in SQL Server. To use geometry, configure the column type in your model.

b.Property(m => m.Geom)
    .HasColumnType("geometry")

or

[Column(Type = "geometry")]
public Geometry Geom { get; set; }