我正在按照John Papa在他最新的PluralSight课程中概述的方法,使用Angular,Breeze和Web API 2构建SPA.
一切顺利,我可以将信息,更新,插入,删除回服务器.但是我使用的是空间类型,当我尝试更新具有空间类型的实体时,会得到以下错误
An exception of type ‘Newtonsoft.Json.JsonSerializationException’ occurred in
Newtonsoft.Json.dll but was not handled in user codeAdditional information: Error getting value from ‘WellKnownValue’ on
‘System.Data.Entity.Spatial.DbGeometry’.
内部异常似乎指出,WellKnownValue为null,它不是,因为我已经检查发送到服务器的JSON,然后发送到Breeze ContextProvider并使用SaveChanges方法保存Well事实.
{
"entities": [
{
"TableKey": 2,"CaseName": "Mikhail Lermontov","StartDate": "2013-06-11T00:00:00Z","EndDate": null,"IsCurrent": true,"SRID": 109,"Shape": {
"$id": "2","$type": "System.Data.Entity.Spatial.DbGeometry,EntityFramework","Geometry": {
"$id": "3","$type": "System.Data.Entity.Spatial.DbGeometryWellKnownValue,"CoordinateSystemId": 2193,"WellKnownText": "POLYGON ((1695943 5462665,1713098 5462665,1713098 5449659,1695943 5449659,1695943 5462665))"
}
},"SpillLocation": "Marlborough Sounds","Image": "http://www.nzmaritime.co.nz/images/lm5.jpg\r\n","DefaultBaseMapKey": 2,"__unmapped": {
"isPartial": false
},"entityAspect": {
"entityTypeName": "DatSpillCase:#Osiris.Model","defaultResourceName": "DatSpillCases","entityState": "Modified","originalValuesMap": {
"CaseName": "Mikhail Lermontov"
},"autoGeneratedKey": {
"propertyName": "TableKey","autoGeneratedKeyType": "Identity"
}
}
}
],"saveOptions": {}
}
所以我的问题是,可以在NewtonSoft库中反序列化DbGeometry类型,如果没有,那么有什么建议可以解决.
解决方法
System.Data.Spatial.DbGeometry不能很好地与Newtonsoft.Json
您需要创建一个JsonConverter来转换DbGeometry
public class DbGeometryConverter : JsonConverter
{
public override bool CanConvert(Type objectType)
{
return objectType.IsAssignableFrom(typeof(string));
}
public override object ReadJson(JsonReader reader,Type objectType,object existingValue,JsonSerializer serializer)
{
JObject location = JObject.Load(reader);
JToken token = location["Geometry"]["WellKnownText"];
string value = token.ToString();
DbGeometry converted = DbGeometry.PolygonFromText(value,2193);
return converted;
}
public override void WriteJson(JsonWriter writer,object value,JsonSerializer serializer)
{
// Base serialization is fine
serializer.Serialize(writer,value);
}
}
[JsonConverter(typeof(DbGeometryConverter))]
public DbGeometry Shape { get; set; }
现在,当您点击BreezeController时,反序列化将由我们的新DbGeometryConverter处理.
希望它有帮助.
