Sql server 使用DbGeography距离和实体框架时响应为空

我知道我的数据库包含一篇具有以下两个属性的文章：

latitude:  44.611589
longitude: -122.215347

我正在写一个方法来查找数据库中距离该位置50.0米以内的所有帖子。（因此，在这种情况下，因为有一个具有这些精确坐标的柱，它的距离为0米，应该包括在内）

这是我的密码：

DbGeography queryLocation = DbGeography.FromText("POINT(-122.215437 44.611589)", 4326);

double d = (double) DbGeography.FromText(
            "POINT(-122.215347 44.611589)"
            , 4326)
            .Distance(queryLocation);

//d is equal to 0 when I execute this, as expected.

IQueryable<Post> posts = db.Posts.Where(p => (double) DbGeography.FromText(
            "POINT(" + SqlFunctions.StringConvert(p.Longitude) + " " + SqlFunctions.StringConvert(p.Latitude) + ")"
            , 4326).Distance(queryLocation) <= 50.0);

//posts is an empty collection when this executes.

这将正确返回具有正确lat/long值的post。因此，我认为假定

SqlFunctions.StringConvert（）

不起作用是公平的，但我没有办法测试它，因为它似乎在LINQ表达式之外不起作用。此外，String.format和double.toString（）在LINQ表达式中不起作用

确认，这是SqlFunctions.StringConvert（）的问题

---

因此，从技术上讲，我可以编写自己的SQL。耶。现在有没有办法通过LINQ到实体来实现这一点？

请尝试PointFromText而不是FromText:

DbGeography queryLocation = DbGeography.PointFromText("POINT(-122.215437 44.611589)", 4326);

double d = (double) DbGeography.PointFromText(
            "POINT(-122.215347 44.611589)"
            , 4326)
            .Distance(queryLocation);

//d is equal to 0 when I execute this, as expected.

IQueryable<Post> posts = db.Posts.Where(p => (double) DbGeography.PointFromText(
            "POINT(" + SqlFunctions.StringConvert(p.Longitude) + " " + SqlFunctions.StringConvert(p.Latitude) + ")"
            , 4326).Distance(queryLocation) <= 50.0);

DbGeography queryLocation=DbGeography.PointFromText（“POINT（-122.215437 44.611589）”，4326；
double d=（double）DbGeography.PointFromText(
“点（-122.215347 44.611589）”
, 4326)
.距离（查询位置）；
//当我执行此操作时，d等于0，如预期的那样。
IQueryable posts=db.posts.Where（p=>（double）DbGeography.PointFromText(
“点（“+SqlFunctions.StringConvert（p.Latitude）+”“+SqlFunctions.StringConvert（p.Latitude）+”“”
距离（查询位置）
var posts = db.Posts
            .Where(p => (double) DbGeography.FromText(
            "POINT(" + SqlFunctions.StringConvert(-122.215347) + " " + SqlFunctions.StringConvert(47.611589) + ")"
            , Constants.MetersCoordinateSystemId)
            .Distance(queryLocation) <= 50.0);

SELECT 
    [Extent1].[Id] AS [Id], 
    [Extent1].[UserId] AS [UserId], 
    [Extent1].[Latitude] AS [Latitude], 
    [Extent1].[Longitude] AS [Longitude]
    FROM [dbo].[Posts] AS [Extent1]
    WHERE (geography::STGeomFromText(N'POINT(' + STR(cast(-122.215347 as float(53))) + N' ' + STR(cast(44.611589 as float(53))) + N')', 4326).STDistance(@p__linq__0)) <= cast(50 as float(53))

SELECT 
    [Extent1].[Id] AS [Id], 
    [Extent1].[UserId] AS [UserId], 
    [Extent1].[Latitude] AS [Latitude], 
    [Extent1].[Longitude] AS [Longitude]
    FROM [dbo].[Posts] AS [Extent1]
    WHERE (geography::STGeomFromText(N'POINT(' + LTRIM(Str(-122.215347, 25, 5)) 
+ N' ' + LTRIM(Str(44.611589, 25, 5)) + N')', 4326).STDistance(geography::STGeomFromText(N'POINT(-122.215347 47.611589)',4326)) <= 50)

DbGeography queryLocation = DbGeography.PointFromText("POINT(-122.215437 44.611589)", 4326);

double d = (double) DbGeography.PointFromText(
            "POINT(-122.215347 44.611589)"
            , 4326)
            .Distance(queryLocation);

//d is equal to 0 when I execute this, as expected.

IQueryable<Post> posts = db.Posts.Where(p => (double) DbGeography.PointFromText(
            "POINT(" + SqlFunctions.StringConvert(p.Longitude) + " " + SqlFunctions.StringConvert(p.Latitude) + ")"
            , 4326).Distance(queryLocation) <= 50.0);