Loading polygons from MS SQL cause "shell is empty but holes are not"

[tcihak-fqa]

Description

I have some simple polygons stored in a MS SQL (geography column) that the database says are valid.
However, NetTopology cannot load them. The exception ("shell is empty but holes are not") is thrown.

Geography value
0xE6100000022405000000DB909E2D6D6F474001000020175A444014E5081BA266474001000020175A444014E5081BA26647400100002037494440DB909E2D6D6F47400100002037494440DB909E2D6D6F474001000020175A444001000000010000000001000000FFFFFFFF0000000003

WKT
POLYGON ((40.703830718994148 46.870519354271629, 40.703830718994148 46.801822070449049, 40.571994781494148 46.801822070449049, 40.571994781494148 46.870519354271629, 40.703830718994148 46.870519354271629))

System Configuration

NetTopology Suite 3.1.3
EF Core 3.1.3
.NET Core 3.1

[kludcev]

Same problem here.

Geography:
0xE610000002240B0000003934D83FED413CC06F01A529002B634039C0F417DE403CC0D14A3D7E122B6340FFCAEEA178403CC0DF9C86C23A2B634043501E89F9403CC06D2EE069612B634014F8FD237E413CC0102CDEB36C2B6340E51277F245423CC0C197CF7B6F2B6340E82EC71655433CC05D4E37275D2B6340C602148ABA433CC051FCEDE2342B634032FE38A639433CC0C66A943B0E2B6340410C810DB5423CC0206D96F1022B63403934D83FED413CC06F01A529002B634001000000010000000002000000FFFFFFFF0000000006000000000000000003

WKT:
MULTIPOLYGON (((153.34376985767037 -28.257526388439349, 153.34600746127265 -28.253388879064207, 153.35092283526953 -28.251840706633626, 153.35564130578442 -28.253807611370814, 153.35701936142914 -28.255831002716221, 153.35735884232966 -28.258879808493379, 153.35512123872732 -28.263017104748457, 153.3502058647305 -28.264565114865739, 153.3454873942157 -28.2625984086173, 153.34410933857089 -28.260575145726992, 153.34376985767037 -28.257526388439349)))

geography.IsValidDetailed() :
24400: Valid

System Configuration

.NET Core 3.1
NetTopology Suite 2.0.0.
EF Core 3.1.3

[kludcev]

Never mind my previous message, I figured my problem out. It was caused by clockwise ring orientation.
Possible solutions in case if someone is interested:
SQL:

Update Table_name 
set Shape = Shape.ReorientObject()
where Shape.EnvelopeAngle() > 90

C#:

if (!polygon.Shell.IsCCW)
      polygon = (Polygon)polygon.Reverse();

[tcihak-fqa]

Thanks @kludcev. I ran the SQL query to fix the shapes.

[airbreather]

Duplicate of NetTopologySuite/NetTopologySuite.IO.SqlServerBytes#9

[alanmachadouk]

For me the SQL @kludcev provided didn't fix the issues in my case as I had a mixture of good and bad orientations and there was no way to tell which was which (the bad records returned angle < 90). Had thousands of records, the error kept appearing. I had geography columns as well.

I finally came up with the SQL that worked for me and fixed the issue, hope it helps someone.

Please test first as this was done on a very simple polygon.

UPDATE <table>
   SET [Boundary] = CONVERT(geography, CONVERT(geometry, [Boundary].STAsText()).MakeValid().STAsText()).MakeValid()
FROM <Table>

The extra MakeValid() at the end may be over kill but hey ho

[SheldonHage]

I've been struggling with this issue ('shell is empty but holes are not') and if only (...if...only...) there was a way to map a SQL Server geography column to an EF type that could then map back to SQL Server. By mapping a Geography column to an NTS Geometry type, I am then unable to use C# to fix the geography and update. At least I don't know of a way. Is there one?

[FObermaier]

You need to use a GeometryFactoryEx to create your geometries. For it you can define the expected orientation for exterior rings. The orientation of the interior rings is opposite, except when the orientation of exterior rings is not explicit.

[callynch]

I am trying to write an empty polygon to an SQL Server geography column, and none of the above worked for me. Both emptyPoly.Shell.IsCCW and emptyPoly.Reverse().Shell.IsCCW return false. Even if I use GeometryFactoryEx with an explicit ring orientation of CCW, the orientation still reports as clockwise and SQL Server will not accept it.

Can anyone tell me how I can construct an empty polygon and then write it to SQL Server?