Postgres SRID - gecko-8/devwiki GitHub Wiki
The Npgsql EF provider defaults columns to SRID of 0. I haven’t been able to find a way to change this so it’s important to create new data points in the following way.
var geometryFactory = NtsGeometryServices.Instance.CreateGeometryFactory(srid: 0);
objUpdate.CurrentLocation = geometryFactory.CreatePoint(new GeoAPI.Geometries.Coordinate(location.Long, location.Lat));
Note the srid: 0 in the factory instance creation.