JSON.Net JsonConverter为DbGeography [英] JSON.Net JsonConverter for DbGeography
问题描述
很久的斗争与此...
Long long struggles with this...
基本上我有一个 DbGeography 属性模型的第一EF5对象。我想申请一个 JsonConverter ，它可以让它往返简单纬度/经度值。我使用的WebAPI。
Basically I have a model-first EF5 object with a DbGeography property. I would like to apply a JsonConverter that let's it roundtrip as simple latitude/longitude values. I'm using WebAPI.
寻找JSON输出和输入，像这样：
Looking for JSON output and input like so:
{
"location":
{
"geopoint":
{
"latitude":40.770712,
"longitude":-73.962011
}
}
}
下面是我的类定义和JsonConverter：
Here is my class definition and JsonConverter:
[MetadataType(typeof(QueryLocationMetadata))]
partial class Location
{
}
public class QueryLocationMetadata
{
[JsonConverter(typeof(DbGeographyConverter))]
public virtual DbGeography GeoPoint { get; set; }
}
public class DbGeographyConverter : JsonConverter
{
private const string LATITUDE_KEY = "latitude";
private const string LONGITUDE_KEY = "longitude";
public override bool CanConvert(Type objectType)
{
return objectType.Equals(typeof(DbGeography));
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
if (reader.TokenType == JsonToken.Null)
return default(DbGeography);
var jObject = JObject.Load(reader);
if (!jObject.HasValues || (jObject.Property(LATITUDE_KEY) == null || jObject.Property(LONGITUDE_KEY) == null))
return default(DbGeography);
string wkt = string.Format("POINT({1} {0})", jObject[LATITUDE_KEY], jObject[LONGITUDE_KEY]);
return DbGeography.FromText(wkt, DbGeography.DefaultCoordinateSystemId);
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
var dbGeography = value as DbGeography;
serializer.Serialize(writer, dbGeography == null || dbGeography.IsEmpty ? null : new { latitude = dbGeography.Latitude.Value, longitude = dbGeography.Longitude.Value });
}
}
所以使用这个，我能够成功地正确序列化和反序列化，甚至一个对象但在此之前我曾经打我的 ApiController 动作我得到以下错误：
System.Data.SqlTypes.SqlNullValueException: Data is Null. This method or property cannot be called on Null values.
at System.Data.SqlTypes.SqlDouble.get_Value()
at GetValueFromSqlDouble(Object )
at System.Web.Http.Metadata.Providers.AssociatedMetadataProvider`1.<>c__DisplayClass3.<GetMetadataForPropertiesImpl>b__0()
at System.Web.Http.Metadata.ModelMetadata.get_Model()
at System.Web.Http.Validation.DefaultBodyModelValidator.ValidateNodeAndChildren(ModelMetadata metadata, ValidationContext validationContext, Object container)
at System.Web.Http.Validation.DefaultBodyModelValidator.ValidateProperties(ModelMetadata metadata, ValidationContext validationContext)
at System.Web.Http.Validation.DefaultBodyModelValidator.ValidateNodeAndChildren(ModelMetadata metadata, ValidationContext validationContext, Object container)
at System.Web.Http.Validation.DefaultBodyModelValidator.ValidateProperties(ModelMetadata metadata, ValidationContext validationContext)
at System.Web.Http.Validation.DefaultBodyModelValidator.ValidateNodeAndChildren(ModelMetadata metadata, ValidationContext validationContext, Object container)
at System.Web.Http.Validation.DefaultBodyModelValidator.ValidateProperties(ModelMetadata metadata, ValidationContext validationContext)
at System.Web.Http.Validation.DefaultBodyModelValidator.ValidateNodeAndChildren(ModelMetadata metadata, ValidationContext validationContext, Object container)
at System.Web.Http.Validation.DefaultBodyModelValidator.ValidateProperties(ModelMetadata metadata, ValidationContext validationContext)
at System.Web.Http.Validation.DefaultBodyModelValidator.ValidateNodeAndChildren(ModelMetadata metadata, ValidationContext validationContext, Object container)
at System.Web.Http.Validation.DefaultBodyModelValidator.ValidateElements(IEnumerable model, ValidationContext validationContext)
at System.Web.Http.Validation.DefaultBodyModelValidator.ValidateNodeAndChildren(ModelMetadata metadata, ValidationContext validationContext, Object container)
at System.Web.Http.Validation.DefaultBodyModelValidator.ValidateProperties(ModelMetadata metadata, ValidationContext validationContext)
at System.Web.Http.Validation.DefaultBodyModelValidator.ValidateNodeAndChildren(ModelMetadata metadata, ValidationContext validationContext, Object container)
at System.Web.Http.Validation.DefaultBodyModelValidator.ValidateElements(IEnumerable model, ValidationContext validationContext)
at System.Web.Http.Validation.DefaultBodyModelValidator.ValidateNodeAndChildren(ModelMetadata metadata, ValidationContext validationContext, Object container)
at System.Web.Http.Validation.DefaultBodyModelValidator.Validate(Object model, Type type, ModelMetadataProvider metadataProvider, HttpActionContext actionContext, String keyPrefix)
at System.Web.Http.ModelBinding.FormatterParameterBinding.<>c__DisplayClass1.<ExecuteBindingAsync>b__0(Object model)
at System.Threading.Tasks.TaskHelpersExtensions.<>c__DisplayClass36`1.<>c__DisplayClass38.<Then>b__35()
at System.Threading.Tasks.TaskHelpersExtensions.<>c__DisplayClass49.<ToAsyncVoidTask>b__48()
at System.Threading.Tasks.TaskHelpers.RunSynchronously[TResult](Func`1 func, CancellationToken cancellationToken)
玩弄周围，谷歌搜索各种各样的事情后，我绝对处于亏损状态。我得到的，一般它正试图验证的属性，但一个SqlDouble？
After toying around and googling all sorts of things, I am absolutely at a loss. I get that in general it is attempting to validate the property but a SqlDouble?
推荐答案
这个问题是不是与你的转换器。这是一个已知的验证问题，当一个公共属性的getter对象图中抛出这种情况发生。这项工作项跟踪问题：
The issue isn't with your converter. This is a known validation bug that happens when a public property's getter throws in the object graph. This work item tracks the issue:
<一个href=\"http://aspnetwebstack.$c$cplex.com/workitem/740\">http://aspnetwebstack.$c$cplex.com/workitem/740
在此同时，你应该能够通过禁用验证绕过它：
In the mean time, you should be able to get around it by disabling validation:
config.Services.Clear(typeof(ModelValidatorProvider));
很抱歉给您带来的不便。
Sorry for the inconvenience.
这篇关于JSON.Net JsonConverter为DbGeography的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
