DbGeography - select polygons/linestrings contained inside polygon - sql-server

Question

I have a case where I want to load map objects located inside users viewport.
This is how I create users viewport rectangle:
DbGeography viewport_rectangle = DbGeography.FromText(string.Format("POLYGON(({0} {1}, {0} {2}, {3} {2}, {3} {1}, {0} {1}))", lon_min, lat_min, lat_max, lon_max));
Then I want to select all objects (Points, PolyLines, Polygons, located inside that rectangle):
var objects = db.mapobjects.Where(x => !x.LocationGeographic.Intersects(viewport_rectangle));
Everything until here works fine. The problem occours if PolyLine/Polygon is not entirely contained inside the viewport polygon. In this case it's ignored and I get "no objects" instead of objects, where some points/edges are out of the viewport.
Is there any alternative to "Intersects"? I want to select objects contained in the viewport rectangle, regardless if they are inside at all, or if only one small part of them is inside of the viewport rectangle.
viewport_rectangle = {SRID=4326;POLYGON ((15.693584159016611
46.532346466357438, 15.693584159016611 46.532770863495614, 15.695530101656916 46.532770863495614, 15.695530101656916 46.532346466357438, 15.693584159016611 46.532346466357438))}
Object which is only partially located inside viewport_rectangle and should be returned as a result:
LINESTRING (15.694189164787527 46.532622094224166, 15.694309193640944
46.532614944062828, 15.694392677396532 46.5326121762582, 15.694401059299702 46.532662919320614, 15.694536175578829 46.532621632923423, 15.694564338773485 46.532659690218026, 15.694584455341097 46.532614944062828, 15.694570373743769 46.532578039989573, 15.694489236921068 46.53258611275777, 15.694502312690016 46.532539290685662, 15.694723930209872 46.53252614359414, 15.69474438205361 46.532575041532539, 15.694786962121723 46.532516225610692, 15.694763492792843 46.532481858630774, 15.694699790328738 46.532507922181281, 15.694884862750767 46.532493852478581, 15.694849658757446 46.53254505695287)
One part of LINQ generated query:
SELECT
[Filter1].[ObjectId] AS [ObjectId],
[Filter1].[LocationGeographic] AS [LocationGeographic],
FROM (SELECT [Extent1].[ObjectId] AS [ObjectId], [Extent1].[LocationGeographic] AS [LocationGeographic]
FROM [dbo].[mapobjects] AS [Extent1]
WHERE (([Filter1].[LocationGeographic].STIntersects(#p__linq__0)) <> cast(1
as bit))
) AS [Project1]
Edited:
the correct order of viewport_rectangle should be:
DbGeography viewport_rectangle = DbGeography.FromText(string.Format("POLYGON(({0} {1}, {2} {1}, {2} {3}, {0} {3}, {0} {1}))", lon_min, lat_min, lon_max, lat_max));

Answer 1

You appear to have a ring orientation problem with your polygon. The order in which you specify your points matters. The polygon, as you've defined it, is the entire globe minus a very small square (presumably, your desired viewport). How did I determine this?
declare #line geography = geography::STGeomFromText('LINESTRING (15.694189164787527 46.532622094224166, 15.694309193640944 46.532614944062828, 15.694392677396532 46.5326121762582, 15.694401059299702 46.532662919320614, 15.694536175578829 46.532621632923423, 15.694564338773485 46.532659690218026, 15.694584455341097 46.532614944062828, 15.694570373743769 46.532578039989573, 15.694489236921068 46.53258611275777, 15.694502312690016 46.532539290685662, 15.694723930209872 46.53252614359414, 15.69474438205361 46.532575041532539, 15.694786962121723 46.532516225610692, 15.694763492792843 46.532481858630774, 15.694699790328738 46.532507922181281, 15.694884862750767 46.532493852478581, 15.694849658757446 46.53254505695287)', 4236),
#poly geography = geography::STGeomFromText('POLYGON ((15.693584159016611 46.532346466357438, 15.693584159016611 46.532770863495614, 15.695530101656916 46.532770863495614, 15.695530101656916 46.532346466357438, 15.693584159016611 46.532346466357438))', 4236);
select #poly.EnvelopeAngle(); --returns 180
select #poly.ReorientObject().STIntersects(#line); --returns 1
Best you read up on the EnvelopeAngle() method yourself. But I'll say this - I use it as a quick heuristic to detect the ring orientation problem you have here. Invariably, if a polygon has this problem, the envelope angle will be 180 (which is almost never what you intended).
I've also given away the punchline on how to fix it in the code above; calling ReorientObject() on the polygon changes clockwise to counterclockwise (and vice versa).
Finally, it looks like your line string was fully contained within your viewport; I tested with STContains(). Which explains why you were getting false before when what you thought was your viewport was everything but the viewport!