c# - 数据库地理类型 MakeValid 似乎不起作用

Question

我有一个应用程序，用户可以在其中绘制区域，稍后我会检查折线是否穿过它们。

应用程序突然崩溃并出现错误:

A .NET Framework error occurred during execution of user-defined routine or aggregate "geography": 
System.ArgumentException: 24144: This operation cannot be completed because the instance is not valid. Use MakeValid to convert the instance to a valid instance. Note that MakeValid may cause the points of a geometry instance to shift slightly.
System.ArgumentException: 
  at Microsoft.SqlServer.Types.SqlGeography.STIntersects(SqlGeography other)

我对消息“使用 MakeValid”感到惊讶，因为我正在使用“MakeValid”，如下所示:

Select ZonePolygonId, ZoneName, isHome  FROM dbo.SpatialZonePolygons 
WHERE Coordinates.STIntersects(geography::STGeomFromText('LINESTRING(51.15826 -0.18398, 51.15855 -0.18404, 51.15883 -0.18414, 51.15903 -0.18427, 51.15915 -0.18437, 51.15922 -0.1845, 51.15918 -0.18493, 51.15882 -0.18748, 51.15975 -0.18783, 51.15994 -0.18793, 51.16056 -0.18846, 51.16055 -0.1885, 51.16054 -0.1886, 51.16057 -0.18877, 51.16061 -0.18884, 51.16067 -0.18888, 51.16072 -0.18889, 51.16078 -0.18888, 51.16086 -0.18878, 51.1609 -0.18861, 51.16087 -0.18843, 51.16085 -0.1884, 51.16175 -0.18677, 51.16203 -0.18625, 51.16227 -0.18587, 51.16246 -0.18566, 51.16263 -0.18552, 51.16319 -0.18513, 51.16333 -0.18502, 51.16351 -0.18481, 51.16362 -0.18462, 51.16371 -0.18437, 51.1638 -0.18386, 51.1643 -0.18029, 51.16466 -0.17755, 51.16466 -0.17715, 51.16458 -0.17674, 51.16441 -0.17635, 51.16414 -0.17593, 51.16386 -0.17558, 51.16367 -0.17538, 51.16369 -0.17534, 51.16372 -0.17524, 51.16371 -0.17514, 51.16369 -0.17505, 51.16365 -0.17498, 51.16359 -0.17494, 51.16354 -0.17493, 51.16351 -0.17494, 51.16348 -0.17482, 51.16346 -0.17473, 51.16341 -0.17459, 51.16278 -0.17353, 51.16262 -0.17324, 51.16255 -0.17308, 51.16254 -0.17298, 51.16256 -0.17275, 51.16282 -0.17248, 51.16305 -0.1723, 51.16321 -0.17222, 51.16334 -0.17219, 51.16347 -0.17219, 51.16367 -0.17225, 51.16385 -0.17237, 51.16403 -0.17256, 51.16427 -0.17292, 51.16459 -0.17345, 51.16476 -0.17363, 51.16665 -0.17706, 51.16728 -0.17817, 51.16728 -0.17823, 51.1673 -0.17835, 51.16734 -0.17842, 51.16741 -0.17851, 51.16747 -0.17854, 51.16756 -0.17853, 51.16765 -0.17845, 51.16771 -0.17831, 51.16772 -0.17815, 51.16771 -0.17807, 51.16776 -0.17743, 51.16798 -0.1769, 51.16831 -0.17611, 51.16848 -0.17578, 51.16881 -0.17529, 51.16925 -0.17463, 51.16976 -0.17384, 51.17095 -0.17214, 51.171 -0.17225, 51.17097 -0.17278, 51.17131 -0.1729, 51.17149 -0.17297, 51.17161 -0.17296, 51.1719 -0.17276, 51.172 -0.17265, 51.17208 -0.17246, 51.1722 -0.17178, 51.17225 -0.17151, 51.17229 -0.17143, 51.17241 -0.17132, 51.17272 -0.17129, 51.17297 -0.17124, 51.17332 -0.17118, 51.17341 -0.17118, 51.17347 -0.17124, 51.17352 -0.17136, 51.17368 -0.17199', 4326).MakeValid())>0

我后来发现有问题的多边形(见图片)绘制得非常糟糕，我猜这是导致问题的原因。

所以我的具体问题是:

1. 我是否正确使用了 MakeValid？我以为 MakeValid() 会解决这种事情...
2. 显然我无法控制客户的绘图技巧，所以如果 MakeValid 对绘制糟糕的多边形没有帮助，是否有其他方法，呃...使其有效？

非常感谢。

Answer 1

好的，所以问题确实是数据库中保存的无效多边形区域。

错误消息中的“使用 MakeValid”触发了一些错误的假设，因为我已经在使用 MakeValid()。实际上，此错误是由无效的多边形区域触发的，而不是我在查询中使用的折线。

为了防止这种情况发生，我在 INSERT SQL 语句中添加了 MakeValid()，这样数据库中就不会再存在无效的多边形了。

我已经测试了在 INSERT 语句中插入带有和不带有“MakeValid”的无效多边形，并且可以确认添加“MakeValid”确实解决了问题。

INSERT INTO SpatialZonePolygons (ZoneName,Coordinates) VALUES ('ValidZone',geography::STGeomFromText('POLYGON([SqlFormattedCoordinates here])', 4326).MakeValid())