相关疑难解决方法(0)

更新:对于tl; dr版本跳到底部

我有一个非常简单的JsonConverter子类,我正在使用Web API:

public class DbGeographyJsonConverter : JsonConverter
{
    public override bool CanConvert(Type type)
    {
        return typeof(DbGeography).IsAssignableFrom(type);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        var value = (string)reader.Value;

        if (value.StartsWith("POINT", StringComparison.OrdinalIgnoreCase))
        {
            return DbGeography.PointFromText(value, DbGeography.DefaultCoordinateSystemId);
        }
        else if (value.StartsWith("POLYGON", StringComparison.OrdinalIgnoreCase))
        {
            return DbGeography.FromText(value, DbGeography.DefaultCoordinateSystemId);
        }
        else //We don't want to support anything else right now.
        {
            throw new ArgumentException();
        }
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        serializer.Serialize(writer, …

我试图从数据库中获取Spartial数据,然后将其序列化(工作得很好).当我尝试反序列化该数据时,抛出JsonSerializationException.

DbGeography geoPoint = CreatePoint(40.7056308, -73.9780035);
string serializedPoint = JsonConvert.SerializeObject(geoPoint);
DbGeography resjson = JsonConvert.DeserializeObject<DbGeography>(serializedPoint);

这是CreatePoint方法:

public static DbGeography CreatePoint(double latitude, double longitude)
{
string text = string.Format(CultureInfo.InvariantCulture.NumberFormat,
"POINT({0} {1})", longitude, latitude);
return DbGeography.PointFromText(text, 4326);
}

我在控制台应用程序中生成了此错误.

Nuget Packages installed: 
EntityFramework 6.1.0
Newtonsoft.Json 6.0.3

有谁知道我做错了什么？