Question

我正在使用DbGeography Entity Framework 6使用此模型：

public class County
{
    public int Id { get; set; }

    public string Name { get; set; }

    public string Code { get; set; }

    public DbGeography Area { get; set; }

}

然后我尝试执行如下Intersects方法：

public County GetCurrentCounty(double latitude, double longitude)
{  
    var point = DbGeography.PointFromText(
        "POINT("
        + longitude.ToString(CultureInfo.InvariantCulture) + " "
        + latitude.ToString(CultureInfo.InvariantCulture) + ")",
        4326);

    var area = db.Counties.FirstOrDefault(x =>
        point.Intersects(x.Area));


    var area1 = db.Counties.FirstOrDefault(x =>
        x.Area.Intersects(point));
}

但是，对于这两种方法，创建的查询都是这样的。我可以做些什么来不选择整个表并在数据库中执行查询？

SELECT 
    [Extent1].[Id] AS [Id], 
    [Extent1].[Name] AS [Name], 
    [Extent1].[Code] AS [Code], 
    [Extent1].[Area] AS [Area]
    FROM [Election].[County] AS [Extent1]

Answer 1

无法说明错误是什么，但第二次显示正确的值。实体框架生成的T-SQL：

SELECT TOP (1) 
[Extent1].[Id] AS [Id], 
[Extent1].[Name] AS [Name], 
[Extent1].[Code] AS [Code], 
[Extent1].[Area] AS [Area]
FROM [Election].[County] AS [Extent1]
WHERE ([Extent1].[Area].STIntersects(@p__linq__0)) = 1


-- p__linq__0: 'POINT (10.0000000 32.0000000)' (Type = Object)

可以手动测试：

declare @p__linq__0 varchar(max)
set @p__linq__0 = 'POINT (10.0000000 32.0000000)' 

SELECT TOP (1) 
    [Extent1].[Id] AS [Id], 
    [Extent1].[Name] AS [Name], 
    [Extent1].[Code] AS [Code], 
    [Extent1].[Area] AS [Area]
    FROM [Election].[County] AS [Extent1]
    WHERE ([Extent1].[Area].STIntersects(@p__linq__0)) = 1

可在此处找到更多信息：

https://docs.microsoft.com/en-us/sql/t-sql/spatial-geometry/stintersects-geometry-data-type

DbGeography相交

1 个答案: