mongodb提供地理位置运算功能，比较常用的场景比如，先判断用户所在的街道，然后看看街道附近有啥餐厅，然后算算用户与餐厅的距离什么的，官网里提供了比较详细的demo介绍不同api的用法
此处记录下dotnet core中的用法
首先安装官网提供的nuget安装包：MongoDB.Driver
定义一个点，线或者多边形进而使用驱动时通常有两种方式，以直线为例：
A.轻松些的方式，可以先获取GeoJsonLineString<GeoJson2DCoordinates>的实例，比较方便，获取实例的方式有两种
1.使用SDK中提供的方法，比如： GeoJson.Point(GeoJson.Position(100.0, 0.0))
2.通过拼接字符串进行反序列化，比如（此处注意“type”属性与里边的值都是指定的而且区分大小写，“coordinates”属性也必须是小写的）：
string lineString = "{ "type" : "LineString", "coordinates" : [[101.0, 0.0], [102.0, 1.0]] }"; GeoJsonLineString<GeoJson2DCoordinates> line = BsonSerializer .Deserialize<GeoJsonLineString<GeoJson2DCoordinates>>(lineString);
B.BsonDocument的方式通常在插入的时候需要得到一个BsonDocument实例，但感觉比较累，不是很喜欢，BsonDocument实例可以通过初始化获得，也可以通过BsonDocument.Parse("")一个json字符串获得,不过位置坐标复杂的情况下比较纠结。
下面以一个判断一个人的坐标在哪个区域为例
先定义一个区域类：
public class AreaPolygon { public int AreaId { set; get; } public string AreaName { set; get; } public GeoJsonPolygon<GeoJson2DCoordinates> Geometry { set; get; } }
然后先插入一条测试数据：
AreaPolygon pp = new AreaPolygon(); pp.AreaName = "Central Harlem North-Polo Grounds"; pp.AreaId = 1; pp.Geometry = BsonSerializer.Deserialize<GeoJsonPolygon<GeoJson2DCoordinates>>(GetPolgon()); var client = new MongoClient("mongodb://localhost:27017"); var database = client.GetDatabase("areadb"); IMongoCollection<AreaPolygon> collection = database.GetCollection<AreaPolygon>("area"); collection.InsertOne(pp);
GetPolgon()方法为一个拼接的多边形:
private string GetPolgon() { var json = "{ 'type' : 'Polygon', 'coordinates' 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}"; var expected = json.Replace("'", """); return expected; }
然后测试下结果：
var point = GeoJson.Point(GeoJson.Position(-73.93414657, 40.82302903)); FilterDefinition<AreaPolygon> find = Builders<AreaPolygon>.Filter.GeoIntersects("Geometry", point); var pro = Builders<AreaPolygon>.Projection.Include("AreaName");//获取结果只包含的字段 var client = new MongoClient("mongodb://localhost:27017"); var database = client.GetDatabase("areadb"); IMongoCollection<AreaPolygon> collection = database.GetCollection<AreaPolygon>("area"); var result= collection.Find(find).Project(pro).FirstOrDefault();
用BsonDocument的方式与此类型，不过对于C#这种静态类型语言，还是直接使用类型泛型比较方便（主要还是辛辛苦苦整理了一份仓储类，然后发现还用用BsonDocument怎么能忍。。。）
BsonDocument bd = new BsonDocument { {"AreaName", "Central Harlem North-Polo Grounds"}, {"AreaId",2 }, {"Geometry",new BsonDocument() { { "type", "Polygon"}, {"coordinates",new BsonArray(){ 73.9557413, 40.7720266 } } } } }; var client = new MongoClient("mongodb://localhost:27017"); var database = client.GetDatabase("areadb"); var collection = database.GetCollection<BsonDocument>("area"); collection.InsertOne(bd); var point = GeoJson.Point(GeoJson.Position(-73.93414657, 40.82302903)); FilterDefinition<BsonDocument> find = Builders<BsonDocument>.Filter.GeoIntersects("Geometry", point); var res = collection.Find(find);
此处coordinates太复杂了是个fload[][][]类型。。。我吓怕了，测试的时候是序列化对象成Json然后在 BsonDocument.Parse(“”)的方式获取的BsonDocument对象，有兴趣可以试试。。;