我在实体框架6.1中使用DbGeography类型与SQL Server 2014,我需要找到可能100,000个实体的最近位置,如下所示逐个执行它是否很慢,是否可以使用类似的方法正如我在下面但是一次完成它们?
<nav class="main-nav">
<a href="index3.html">Home</a>
<a</a>
<a href="contact.html">Contact</a>
<a href="directory.html">Directory</a>
</nav>
原因我说这是因为在此之前,我使用存储过程做了类似的事情。
public List<GeocodableEntity> LinkToRoadNodes(List<GeocodableEntity> entities)
{
foreach (var entity in entities)
{
var nearestLocation = GetNearestLocation(entity.Latitude, entity.Longitude, DEFAULT_ROAD_NODE_LINK_RADIUS);
// update entity with values from nearestLocation
}
return entities;
}
private GeoLocation GetNearestLocation(float latitude, float longitude, double searchRadius)
{
var sourcePoint = Helper.CreateDbGeographyPoint(latitude, longitude);
return Locations.Where(x => x.Point.Distance(sourcePoint) < searchRadius)
.OrderBy(x => x.Point.Distance(sourcePoint))
.FirstOrDefault();
}
@CoordinateList是:
ALTER PROCEDURE [dbo].[GetNearestLocationNodesByCoordinates]
@CoordinateList dbo.CoordinateListWithRefId READONLY
AS
BEGIN
WITH InputCTE AS
(
SELECT RefID, geography::Point(Latitude, Longitude, 4326) AS Point
FROM @CoordinateList
)
SELECT x.RefID, x.NodeId, x.Latitude, x.Longitude, x.LocationTypeId
FROM (SELECT I.RefID as 'RefID',
L.NodeId,
L.Point.Lat as 'Latitude',
L.Point.Long as 'Longitude',
L.LocationTypeId,
ROW_NUMBER() OVER (PARTITION BY I.RefID ORDER BY L.Point.STDistance(I.Point)) AS Ranking
FROM InputCTE AS I
JOIN Location AS L
ON L.Point.STDistance(I.Point) <= 5000) AS x WHERE Ranking = 1
END
如果可能的话,我想在C#代码中执行相同的操作,而无需触及存储过程或键入SQL查询字面值。
EntityFramework.dll中出现“System.InvalidOperationException”类型的异常,但未在用户代码中处理 附加信息:创建模型时无法使用上下文。如果在OnModelCreating方法中使用上下文,或者同时由多个线程访问相同的上下文实例,则可能抛出此异常。请注意,DbContext和相关类的实例成员不保证是线程安全的。