I have a data table containing information related to cities along with the boundaries stored as a polygon. I wrote the following function to convert the data into a JSON file.

public static string DataTableToGeoJSONString(DataTable dataTable)
    {

        var cityData = new
        {
            type = "FeatureCollection",
            features = dataTable.AsEnumerable().Select(record => new {
                type = "Feature",
                id = Convert.ToString(record["Id"]),
                properties = new
                {
                    name = Convert.ToString(record["Name"]),
                    density = Convert.ToInt32(record["NumCri"])
                },
                geometry = new
                {
                    type = "Polygon",
                    coordinates = new [] { 
                       (record["Coordinates"])
                    }   

                },
          
            })
        };
        return JsonConvert.SerializeObject(cityData);
    }

I understand that the polygon is an array of arrays hence the following code statement does not work

    type = "Polygon",
    coordinates = new [] { 
    (record["Coordinates"])

Any advice on how to store the array of arrays into coordinates variable? Please note that the record["Coordinates"] stores the coordinate information in the following format:

[[[23.444,44.444],[24.444,45.222],...]]]

CodePudding user response：

Take a look at this example. It does the following:

1. Parse the literal as an array
2. Get the first item from the array and cast the item from a generic token to an array
3. Loop over every item in the array from step 2
4. Cast the currently iterated item from a generic token to an array
5. Create a new PointF and add it to a collection based on the values of the currently iterated array from step 4

Private Function ParseCoordinates(json As String) As IEnumerable(Of PointF)
    Dim outerArray As JArray = JArray.Parse(json)
    Dim innerArray As JArray = DirectCast(outerArray.Item(0), JArray)
    Dim points As New List(Of PointF)()

    For Each item As JToken In innerArray
        Dim itemArray As JArray = DirectCast(item, JArray)
        points.Add(New PointF(itemArray.Item(0).Value(Of Single)(), itemArray.Item(1).Value(Of Single)()))
    Next

    Return points
End Function

Fiddle: https://dotnetfiddle.net/mAJgfz

Keep in mind that this assumes that your data is perfect. I would highly recommend you take the time to setup some conditional statements to make sure that:

1. The outerArray variable can be parsed to a JArray
2. There are more than 0 items in outerArray before declaring innerArray
3. The innerArray variable can be cast to a JArray
4. The itemArray variable can be cast to a JArray
5. There is more than 1 item in the itemArray variable before setting them as the X/Y values of the PointF
6. The values of itemArray can be cast to a Single