Can't get a simple Entity Framework spatial query to work

Question

This query on my sql server returns lots of rows:

declare @referencepoint Geography = Geography::Point(48.208173, 16.373813, 4326);
SELECT *
FROM myTable
WHERE Location.STDistance(@referencepoint) < 20000

but the equivalent in EF returns none:

DbGeography referencepoint = DbGeography.PointFromText("POINT(48.208173 16.373813)", 4326);
var records = (from r in db.myTable
               where r.Location.Distance(referencepoint ) <= 20000
               select r).ToList();

Looking at the query generated via profiler I see this:

declare @p3 sys.geography
set @p3=convert(sys.geography,0xE6100000010CD4D17135B25F30408274B169A51A4840)

SELECT *
FROM [myTable]
WHERE ([Location].STDistance(@p3)) <= 20000 

Does EF have an issue here, or do I?

Answer 1

OP has the issue here :) Both SQL and EF are working as expected. OP's statement was incorrect.

SQL Point Syntax:

declare @referencepoint Geography = Geography::Point(48.208173, 16.373813, 4326);

is actually equivalent to .Net:

DbGeography referencepoint = DbGeography.PointFromText("POINT(16.373813 48.208173)", 4326);
// Note the parameters are reversed from OP's statement

---

In SQL and EF (.Net) the Geography data type uses a standard WellKnownText notation to define points and polygons and other structures internally.

In WellKnownText format a Point is specified as POINT(X Y) on a Cartesian plane. - Note the lack of a comma, the values are only delimited by a space

When we want to express the location on the earth as a point on a Cartesian plane, the X axis is the equator, the Y axis is then a Meridian line running between the North and South Poles.

Longitute, by definition is the east-west position on the surface of the Earth (so parallel with the equator, the X ordinate)

Latitude, by definition is the north-south position on the surface of the Earth (perpendicular to the equator, the Y ordinate)

Therefore to express a Point on the earth in WellKnownText format as if it were a point on a Cartesian plane we must use this syntax:

POINT(Longitude Latitude)

What confuses the issue is that in most verbal and written forms we refer to Latitude and Longitude in that order, so in SQL we have a helper function that takes the parameters in that order, because this was supposed to make it less confusing. And in a way it is, because the parameters are named appropriately. To further explain the point I have expanded out OP's statements with the correction

SQL

DECLARE @latitude float = 48.208173
DECLARE @longitude float = 16.373813
DECLARE @srid int = 4326
DECLARE @referencepoint Geography = Geography::Point(@latitude, @longitude, @srid);
SELECT *
FROM myTable
WHERE Location.STDistance(@referencepoint) < 20000

.Net

double latitude = 48.208173;
double longitude = 16.373813;
int srid = 4326;
DbGeography referencepoint = DbGeography.PointFromText($"POINT({longitude} {latitude})", srid);
var records = (from r in db.myTable
                where r.Location.Distance(referencepoint) <= 20000
                select r).ToList();

---

I can't even find a good reference explaining why we generally refer to Latitude and Longitude (in that order) I suspect it's based on the fact that LatLon rolls off the tongue better or because latitude was discovered/measured first?