@Mganjirad ODP.NET EF Core Spatial support is available with Oracle.EntityFrameworkCore.NetTopologySuite on NuGet Gallery. It has some limited support for curved geometries.

I've posted an EF Core sample using various Oracle spatial types.

The Oracle SDO_GEOMETRY columns can be represented as NTS Geometry types in EF Core. Let me know if you have any other questions.

@Mganjirad Here are the Oracle team's answers to your questions:

Question

If EF Core + NTS integration attempts to materialize such geometries,
how will this be handled?

Answer

In Oracle Spatial datasets it is possible for a single SDO_GEOMETRY
column to contain both linear and curved geometries. When this column is
mapped to NetTopologySuite (NTS) types in EF Core, the behavior depends
on the type of geometry stored in each row.

• Rows containing linear geometries are materialized normally into NTS types.
• Rows containing curved geometries fail during materialization.

The key reason is already well established: NetTopologySuite itself does
not support curved geometry types. Because of that:

• NetTopologySuite
  does not represent curves.
• NetTopologySuite.IO.Oracle
  only supports geometries composed of straight segments.
• Oracle.EntityFrameworkCore.NetTopologySuite depends directly on
  these libraries, so it inherits the same limitation.

Question

Will ODP.NET automatically linearize these curved geometries when
mapping them to NTS types (which would alter the original geometry)?
Or is there a plan to allow applications to access the raw curved
geometry as-is?

Answer

No. Automatic linearization is not performed, and raw curved geometries
cannot currently be materialized as NTS types because NetTopologySuite
does not support curved geometry types; therefore NetTopologySuite.IO.Oracle and
Oracle.EntityFrameworkCore.NetTopologySuite --- which depend on
NetTopologySuite --- cannot support this scenario either unless curve
support is added to NTS and its Oracle IO layer.

Workarounds

Since curved geometries cannot be directly materialized into NTS types, the following approaches are typically used:

1. Linearize the geometry in SQL before EF reads it

Convert curves to straight segments using SDO_GEOM.SDO_ARC_DENSIFY.

var rows = ctx.SpatialCurves
    .FromSqlRaw(@"
        SELECT s.ID,
               s.NAME,
               SDO_GEOM.SDO_ARC_DENSIFY(s.GEOM, 0.005, 'arc_tolerance=0.05') AS GEOM
        FROM SCOTT.SPATIAL_CURVES s")
    .AsNoTracking()
    .ToList();

2. Use a database view with linearized geometry

Create a read-only view that exposes a linearized version of the
geometry while keeping the base table unchanged.

CREATE OR REPLACE VIEW SCOTT.SPATIAL_CURVES_LINEAR AS
SELECT s.ID,
       s.NAME,
       SDO_GEOM.SDO_ARC_DENSIFY(s.GEOM, 0.005, 'arc_tolerance=0.05') AS GEOM
FROM SCOTT.SPATIAL_CURVES s;

EF Core mapping example

modelBuilder.Entity<SpatialCurf>(b =>
{
    b.ToView("SPATIAL_CURVES_LINEAR", schema: "SCOTT");
    b.HasKey(e => e.Id);

    b.Property(e => e.Geom).HasColumnName("GEOM");
    b.Property(e => e.Name).HasColumnName("NAME");
});

3. Retrieve WKT/WKB instead of NTS geometry

Use Oracle utilities like SDO_UTIL.TO_WKTGEOMETRY or
SDO_UTIL.TO_WKBGEOMETRY and parse them on the client if needed.

Here is some sample code for the suggested workarounds.

Question

In some scenarios, we need to read a curved geometry from the Oracle
table, keep it in its original form, and convert it to WKT in the
application layer before sending it to the client. Since NTS does not
support curved types, how is this expected to be managed? Will there be
an option to bypass NTS for these cases and still work with the raw
SDO_GEOMETRY objects directly?

Answer

No. While EF Core with Oracle.EntityFrameworkCore.NetTopologySuite can
return the WKT representation of a curved geometry from the database, it
cannot convert that WKT into an NTS geometry because NetTopologySuite
does not support curved types; consequently when the application tries
to parse such WKT using WKTReader, it fails with an error like "WKT path
failed: Unknown type: CIRCULARSTRING", and this limitation will remain
until curve support is added to NetTopologySuite and NetTopologySuite.IO.Oracle.

Question

Current EF Core behavior

Just to make sure I understand: if I connect EF Core to an Oracle
Spatial database today, how are SDO_GEOMETRY columns currently
represented in the EF Core model? Do they map to a specific .NET type,
or are they exposed as raw objects that require manual handling?

Answer

When using EF Core with Oracle.EntityFrameworkCore.NetTopologySuite,
SDO_GEOMETRY columns are mapped to types from NetTopologySuite rather
than being exposed as raw objects.

During database scaffolding, the column is typically represented as the
base NTS type Geometry, since a single SDO_GEOMETRY column may contain
mixed geometry types (for example points, lines, or polygons).

In code-first scenarios, developers can use specific NTS derived types
such as Point, LineString, or Polygon in their entity model, and
EF Core will map those properties to the Oracle SDO_GEOMETRY column type
accordingly.

On a side note, there is a GitHub project to support curves in NTS. However, that project has not had a commit in almost 5 years.

I truly cannot thank you and the Oracle team enough. Your detailed, precise, and incredibly helpful answers have been invaluable to me. I deeply appreciate the time you took and the thoughtful guidance you provided. Thank you.