在 GeoJson 对象中包含 JSON 流？

Posted 2023-04-12

【中文标题】在 GeoJson 对象中包含 JSON 流？

【英文标题】：Include JSON stream in GeoJson object?

【发布时间】：2020-02-15 19:40:03

【问题描述】：

我正在学习如何创建GeoJson 流。我知道如何将datatable 转换为 JSON 字符串，然后序列化为 JSON 格式。问题是我不知道如何将此 JSON 流包含在 GeoJson 对象中。

以下代码生成一个geojson对象：

    public geoJson Leaflets_GeoJson()
    

        var CorOrd = new LocalGeometry();
        CorOrd.coordinates = new List<double>(); // <=====
        CorOrd.coordinates.Add(34.2305);
        CorOrd.coordinates.Add(-86.2644);
        CorOrd.type = "Point";

        var myProps = new Properties();
        myProps.name = "John";
        myProps.id = "JN123";
        myProps.address = "Howard Street";


        var geoJson = new geoJson
        
            type = "FeatureCollection",
            features = new List<LocalFeature>
            
               new LocalFeature  type = "Feature", geometry = CorOrd, properties=myProps
            

        ;

        return geoJson;

    

返回以下内容：

"features":["geometry":"coordinates":[18.2305,-66.2644],"type":"Point","properties":"address":"Howard Street","id":"JN123","name":"John","type":"Feature"],"type":"FeatureCollection"

这是采用数据表并返回 JSON 流的方法：

public System.IO.Stream()

    string sqlQuery = string.Format("usp_GetNames");

    string connString = System.Configuration.ConfigurationManager.ConnectionStrings["connstring"].ToString();
    SqlDatabase sqlDatabase = new SqlDatabase(connString);
    DataSet result = sqlDatabase.ExecuteDataSet(CommandType.Text, sqlQuery);


    string callback = JsonConvert.SerializeObject(result.Tables[0]);
    byte[] resultBytes = Encoding.UTF8.GetBytes(callback);
    return new System.IO.MemoryStream(resultBytes);

并返回此JSON:

[
 "name":"Joe","address":"Main Street","id":"Joe121", "Lon": 40.730610, "Lat": -73.935242, 
 "name":"Mary","address":"220 Avenue","id":"Mary625", "Lon": 42.730610, "Lat": -72.935242
]

我的问题：如何将这两个流结合起来，使其返回一个看起来像这样的 GeoJson 对象？

 "type": "FeatureCollection", "features": [ "type": "Feature", "properties": 
   "name":"Joe","address":"Main Street","id":"Joe121","geometry": "type": "Point","coordinates": [-73.1232, 40.7306], 
   "type": "Feature", "properties": "name":"Mary","address":"220 Avenue","id":"Mary625","geometry": "type": "Point","coordinates": [-71.1232, 41.7306]]  

【问题讨论】：

你在使用nettopologysuite吗？如果是这样，请参阅 Having trouble serializing NetTopologySuite FeaturesCollection to GeoJSON 或 How to seed NetTopologySuite.Geometries.Point data from a Json file in ASP.Net core。

我没有使用 nettopologysuite。

【参考方案1】：

您需要将该数组包装在实现两个属性（类型和特性）的外部类中。您可以为此使用 C# 匿名类型：

var envelope = new

    type = "FeatureCollection",
    features = result.Tables[0]
;

string callback = JsonConvert.SerializeObject(envelope);
byte[] resultBytes = Encoding.UTF8.GetBytes(callback);
//...

【讨论】：

谢谢。我试过了。问题是每个都有额外的静态数据。所以在features 中有另一个json 块。坐标也在一个单独的块中："features": [ "type": "Feature", "properties": "name":"Joe","address":"Main Street","id":"Joe121","geometry": "type": "Point","coordinates": [-73.1232, 40.7306]