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#6567 add support for writing GeoJSON with Z values #6602

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51dd2f0
#6567 write geojson with Z
xfischer Jun 9, 2026
e5c89f8
fix indentation
xfischer Jun 9, 2026
446f2b8
readability and tests upated
xfischer Jun 10, 2026
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56 changes: 51 additions & 5 deletions src/Npgsql.GeoJSON/Internal/GeoJSONConverter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -273,7 +273,7 @@ static Position ReadPosition(PgReader reader, EwkbGeometryType type, bool little
var position = new Position(
longitude: ReadDouble(littleEndian),
latitude: ReadDouble(littleEndian),
altitude: HasZ(type) ? reader.ReadDouble() : null);
altitude: HasZ(type) ? ReadDouble(littleEndian) : null);
if (HasM(type)) ReadDouble(littleEndian);
return position;

Expand Down Expand Up @@ -423,16 +423,34 @@ public static ValueTask Write(bool async, PgWriter writer, IGeoJSONObject value,
_ => throw UnknownPostGisType()
};

static bool FirstCoordinateHasZ(IGeoJSONObject value)
=> value switch
{
Point p => HasZ(p.Coordinates),
LineString ls => ls.Coordinates is [var c, ..] && c.Altitude.HasValue,
Polygon poly => poly.Coordinates is [var ring, ..] && ring.Coordinates is [var c, ..] && HasZ(c),
MultiPoint mp => mp.Coordinates is [var p, ..] && FirstCoordinateHasZ(p),
MultiLineString mls => mls.Coordinates is [var l, ..] && FirstCoordinateHasZ(l),
MultiPolygon mpoly => mpoly.Coordinates is [var p, ..] && FirstCoordinateHasZ(p),
GeometryCollection c => c.Geometries is [var g, ..] && FirstCoordinateHasZ((IGeoJSONObject)g),
_ => throw UnknownPostGisType()
};

static async ValueTask Write(bool async, PgWriter writer, Point value, CancellationToken cancellationToken)
{
var type = EwkbGeometryType.Point;
var size = SizeOfHeader;
var srid = GetSrid(value.CRS);
var hasZ = FirstCoordinateHasZ(value);
if (srid != 0)
{
size += sizeof(int);
type |= EwkbGeometryType.HasSrid;
}
if (hasZ)
{
type |= EwkbGeometryType.HasZ;
}

if (writer.ShouldFlush(size))
await writer.Flush(async, cancellationToken).ConfigureAwait(false);
Expand All @@ -443,19 +461,24 @@ static async ValueTask Write(bool async, PgWriter writer, Point value, Cancellat
if (srid != 0)
writer.WriteInt32(srid);

await WritePosition(async, writer, value.Coordinates, cancellationToken).ConfigureAwait(false);
await WritePosition(async, writer, value.Coordinates, hasZ, cancellationToken).ConfigureAwait(false);
}

static async ValueTask Write(bool async, PgWriter writer, LineString value, CancellationToken cancellationToken)
{
var type = EwkbGeometryType.LineString;
var size = SizeOfHeaderWithLength;
var srid = GetSrid(value.CRS);
var hasZ = FirstCoordinateHasZ(value);
if (srid != 0)
{
size += sizeof(int);
type |= EwkbGeometryType.HasSrid;
}
if (hasZ)
{
type |= EwkbGeometryType.HasZ;
}

if (writer.ShouldFlush(size))
await writer.Flush(async, cancellationToken).ConfigureAwait(false);
Expand All @@ -470,19 +493,24 @@ static async ValueTask Write(bool async, PgWriter writer, LineString value, Canc
writer.WriteInt32(srid);

foreach (var t in coordinates)
await WritePosition(async, writer, t, cancellationToken).ConfigureAwait(false);
await WritePosition(async, writer, t, hasZ, cancellationToken).ConfigureAwait(false);
}

static async ValueTask Write(bool async, PgWriter writer, Polygon value, CancellationToken cancellationToken)
{
var type = EwkbGeometryType.Polygon;
var size = SizeOfHeaderWithLength;
var srid = GetSrid(value.CRS);
var hasZ = FirstCoordinateHasZ(value);
if (srid != 0)
{
size += sizeof(int);
type |= EwkbGeometryType.HasSrid;
}
if (hasZ)
{
type |= EwkbGeometryType.HasZ;
}

if (writer.ShouldFlush(size))
await writer.Flush(async, cancellationToken).ConfigureAwait(false);
Expand All @@ -503,7 +531,7 @@ static async ValueTask Write(bool async, PgWriter writer, Polygon value, Cancell
var coordinates = t.Coordinates;
writer.WriteInt32(coordinates.Count);
foreach (var t1 in coordinates)
await WritePosition(async, writer, t1, cancellationToken).ConfigureAwait(false);
await WritePosition(async, writer, t1, hasZ, cancellationToken).ConfigureAwait(false);
}
}

Expand All @@ -517,6 +545,10 @@ static async ValueTask Write(bool async, PgWriter writer, MultiPoint value, Canc
size += sizeof(int);
type |= EwkbGeometryType.HasSrid;
}
if (FirstCoordinateHasZ(value))
{
type |= EwkbGeometryType.HasZ;
}

if (writer.ShouldFlush(size))
await writer.Flush(async, cancellationToken).ConfigureAwait(false);
Expand Down Expand Up @@ -544,6 +576,10 @@ static async ValueTask Write(bool async, PgWriter writer, MultiLineString value,
size += sizeof(int);
type |= EwkbGeometryType.HasSrid;
}
if (FirstCoordinateHasZ(value))
{
type |= EwkbGeometryType.HasZ;
}

if (writer.ShouldFlush(size))
await writer.Flush(async, cancellationToken).ConfigureAwait(false);
Expand Down Expand Up @@ -571,6 +607,10 @@ static async ValueTask Write(bool async, PgWriter writer, MultiPolygon value, Ca
size += sizeof(int);
type |= EwkbGeometryType.HasSrid;
}
if (FirstCoordinateHasZ(value))
{
type |= EwkbGeometryType.HasZ;
}

if (writer.ShouldFlush(size))
await writer.Flush(async, cancellationToken).ConfigureAwait(false);
Expand All @@ -597,6 +637,10 @@ static async ValueTask Write(bool async, PgWriter writer, GeometryCollection val
size += sizeof(int);
type |= EwkbGeometryType.HasSrid;
}
if (FirstCoordinateHasZ(value))
{
type |= EwkbGeometryType.HasZ;
}

if (writer.ShouldFlush(size))
await writer.Flush(async, cancellationToken).ConfigureAwait(false);
Expand All @@ -614,7 +658,7 @@ static async ValueTask Write(bool async, PgWriter writer, GeometryCollection val
await Write(async, writer, (IGeoJSONObject)t, cancellationToken).ConfigureAwait(false);
}

static async ValueTask WritePosition(bool async, PgWriter writer, IPosition coordinate, CancellationToken cancellationToken)
static async ValueTask WritePosition(bool async, PgWriter writer, IPosition coordinate, bool hasZ, CancellationToken cancellationToken)
{
var altitude = coordinate.Altitude;
if (SizeOfPoint(altitude.HasValue) is var size && writer.ShouldFlush(size))
Expand All @@ -624,6 +668,8 @@ static async ValueTask WritePosition(bool async, PgWriter writer, IPosition coor
writer.WriteDouble(coordinate.Latitude);
if (altitude.HasValue)
writer.WriteDouble(altitude.Value);
else if (hasZ)
writer.WriteDouble(0d);
}

static ValueTask BufferData(this PgReader reader, bool async, int byteCount, CancellationToken cancellationToken)
Expand Down
49 changes: 48 additions & 1 deletion test/Npgsql.PluginTests/GeoJSONTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,10 @@ public struct TestData
public string CommandText;
}

public static readonly TestData[] Tests =
/// <summary>The Z coordinate applied to every position when deriving the 3D variants of <see cref="TwoDimensionalTests"/>.</summary>
const double Z = 5d;

static readonly TestData[] TwoDimensionalTests =
[
new()
{
Expand Down Expand Up @@ -107,6 +110,41 @@ public struct TestData
}
];

public static readonly TestData[] Tests =
[
..TwoDimensionalTests,
..TwoDimensionalTests.Select(static t => new TestData
{
Geometry = WithZ(t.Geometry),
CommandText = $"st_force3d({t.CommandText}, {Z})"
})
];

// Derives a 3D copy of a geometry by adding the Z altitude to every position, leaving the originals untouched.
static GeoJSONObject WithZ(GeoJSONObject geometry)
{
static Position AddZ(IPosition p) => new(latitude: p.Latitude, longitude: p.Longitude, altitude: Z);
static LineString Line(LineString line) => new(line.Coordinates.Select(AddZ));

GeoJSONObject result = geometry switch
{
Point point => new Point(AddZ(point.Coordinates)),
LineString line => Line(line),
Polygon polygon => new Polygon(polygon.Coordinates.Select(Line)),
MultiPoint multiPoint => new MultiPoint(multiPoint.Coordinates.Select(pt => new Point(AddZ(pt.Coordinates)))),
MultiLineString multiLine => new MultiLineString(multiLine.Coordinates.Select(Line)),
MultiPolygon multiPolygon => new MultiPolygon(multiPolygon.Coordinates.Select(p => new Polygon(p.Coordinates.Select(Line)))),
GeometryCollection collection => new GeometryCollection(collection.Geometries.Select(g => (IGeometryObject)WithZ((GeoJSONObject)g))),
_ => throw new NotSupportedException($"Unexpected geometry type {geometry.Type}")
};

// A 2D bounding box [minX, minY, maxX, maxY] becomes the 3D form [minX, minY, minZ, maxX, maxY, maxZ].
if (geometry.BoundingBoxes is { } bbox)
result.BoundingBoxes = [bbox[0], bbox[1], Z, bbox[2], bbox[3], Z];

return result;
}

[Test, TestCaseSource(nameof(Tests))]
public async Task Read(TestData data)
{
Expand Down Expand Up @@ -154,6 +192,15 @@ public async Task IgnoreM()
new Position(3d, 3d),
new Position(4d, 4d)
])
},
new()
{
Geometry = new LineString([
new Position(1d, 1d),
new Position(2d, 2d),
new Position(3d, 3d, 10d),
new Position(4d, 4d)
])
}
];

Expand Down
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