Newtonsoft.Json.JsonSerializationException（从“System.Data.SqlTypes.SqlDouble”上的 'Value' 获取值时出错）序列化 SqlGeography

Question

我试图在数据库 SQL 服务器 2012 中使用 Newtonsoft.Json 版本 'Newtonsoft.Json.10.0.3' 将 DataTable 对象序列化为 Json。

table 有一个类型为 'geography' 的列，其中包含类型 SqlGeography.

的实例

用于生成的代码json:

    public string SerializeToJson()
    {

     var connstring1 ="Data Source=server1;Initial Catalog=database1;user=xxx;password=yyy";
        var sql = "SELECT  * FROM table_1 "; //table_1 has a column of type geography
        using (var c1 = new SqlConnection(connstring1))
        {
            c1.Open();
            var da = new SqlDataAdapter()
            {
                SelectCommand = new SqlCommand(sql, c1)
            };

            DataSet ds1 = new DataSet("table");
            da.Fill(ds1, "table");
            var dt = ds1.Tables[0];

            //serialize to Json

            try
            {
                var options = new JsonSerializerSettings
                {
                    Formatting = Formatting.None
                };
                //this line fire exception for geography type
                var json = JsonConvert.SerializeObject(dt, options);
                return json;
            }
            catch (Exception ex)
            {

                Console.WriteLine(ex);
            }                
        }
    }

我已经从 sql 2012

的功能包中安装了程序集 'Microsoft.SqlServer.Types'

我创建了一个完整的 C# 程序（独立于 sql 服务器安装），使用带有 SqlGeography 列的数据table 来显示问题 Try it

我收到错误：

Newtonsoft.Json.JsonSerializationException: Error getting value from 'Value' on 'System.Data.SqlTypes.SqlDouble'. --->

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 GetValue(Object ) at Newtonsoft.Json.Serialization.DynamicValueProvider.GetValue(Object target)

我达到了https://github.com/JamesNK/Newtonsoft.Json/issues/993，但没办法。

解决问题的任何帮助。

编辑：

根据@dbc 的评论，我提供了用于生成 json.

的完整源代码

完整的错误信息是：

Newtonsoft.Json.JsonSerializationException: Error getting value from 'Value' on 'System.Data.SqlTypes.SqlDouble'. ---> >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 GetValue(Object ) at Newtonsoft.Json.Serialization.DynamicValueProvider.GetValue(Object target)

--- End of inner exception stack trace --- at Newtonsoft.Json.Serialization.DynamicValueProvider.GetValue(Object target)

at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.CalculatePropertyValues(JsonWriter writer, Object value, JsonContainerContract contract, JsonProperty member, JsonProperty property, JsonContract& memberContract, Object& memberValue) at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeObject (JsonWriter writer, Object value, JsonObjectContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty) at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue( JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member , JsonContainerContract containerContract, JsonProperty containerProperty) at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeObject (JsonWriter writer, Object value, JsonObjectContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty) at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue( JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member , JsonContainerContract containerContract, JsonProperty containerProperty) at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize(JsonWriter jsonWriter, Object value, Type objectType) at Newtonsoft.Json.Serialization.JsonSerializerProxy.SerializeInternal(JsonWriter jsonWriter, Object value, Type rootType) at Newtonsoft.Json.Converters.DataTableConverter.WriteJson(JsonWriter writer, Object value, JsonSerializer serializer) at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeConver table(JsonWriter writer, JsonConverter converter, Object value, JsonContract contract, JsonContainerContract collectionContract, JsonProperty containerProperty)

at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue( JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member , JsonContainerContract containerContract, JsonProperty containerProperty) at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize(JsonWriter jsonWriter, Object value, Type objectType) at Newtonsoft.Json.JsonSerializer.SerializeInternal(JsonWriter jsonWriter, Object value, Type objectType) at Newtonsoft.Json.JsonConvert.SerializeObjectInternal(Object value, Type type, JsonSerializer jsonSerializer) at Newtonsoft.Json.JsonConvert.SerializeObject(Object value, JsonSerializerSettings settings) at JsonTester.SerializeToJson() in F:\JsonTester.cs:line 104

编辑2：

我按照@dbc 的描述启用跟踪，并得到以下日志：

2017-08-24T19:45:31.941 Info Started serializing System.Data.DataTable with converter Newtonsoft.Json.Converters.DataTableConverter. Path ''.

2017-08-24T19:45:31.972 Info Started serializing Microsoft.SqlServer.Types.SqlGeography. Path '[0].f1'.

2017-08-24T19:45:32.003 Info Started serializing System.Data.SqlTypes.SqlInt32.Path '[0].f1.STSrid'.

2017-08-24T19:45:32.003 Info Finished serializing System.Data.SqlTypes.SqlInt32. Path '[0].f1.STSrid'.

2017-08-24T19:45:32.003 Info Started serializing System.Data.SqlTypes.SqlDouble. Path '[0].f1.Lat'.

2017-08-24T19:45:32.003 Info Finished serializing System.Data.SqlTypes.SqlDouble. Path '[0].f1.Lat'.

2017-08-24T19:45:32.003 Info Started serializing System.Data.SqlTypes.SqlDouble. Path '[0].f1.Long'.

2017-08-24T19:45:32.003 Info Finished serializing System.Data.SqlTypes.SqlDouble. Path '[0].f1.Long'.

2017-08-24T19:45:32.003 Info Started serializing System.Data.SqlTypes.SqlDouble. Path '[0].f1.Z'.

2017-08-24T19:45:32.003 Error Error serializing System.Data.SqlTypes.SqlDouble.Error getting value from 'Value' on 'System.Data.SqlTypes.SqlDouble'.

2017-08-24T19:45:32.003 Error Error serializing System.Data.DataTable. Error getting value from 'Value' on 'System.Data.SqlTypes.SqlDouble'.

Answer 1

看起来 System.Data.SqlTypes 中的 SqlDouble 之类的原始类型似乎不能被 Json.NET 开箱即用地序列化，因为它们没有实现自己的 TypeConverter。来自 docs:

Primitive Types

.Net: TypeConverter (convertible to String)
JSON: String

这将有必要为内置 .Net 类型实现 custom JsonConverter to serialize these types. Json.NET has several built-in converters such as KeyValuePairConverter，所以这并不罕见。

SqlBoolean、SqlBinary、SqlDouble 等不共享公共基础 class 或 INullable 以外的接口这一事实需要一些重复代码：

public static class SqlPrimitiveConverters
{
    public static JsonSerializerSettings AddSqlConverters(this JsonSerializerSettings settings)
    {
        foreach (var converter in converters)
            settings.Converters.Add(converter);
        return settings;
    }

    static readonly JsonConverter[] converters = new JsonConverter[]
    {
        new SqlBinaryConverter(),
        new SqlBooleanConverter(),
        new SqlByteConverter(),
        new SqlDateTimeConverter(),
        new SqlDecimalConverter(),
        new SqlDoubleConverter(),
        new SqlGuidConverter(),
        new SqlInt16Converter(),
        new SqlInt32Converter(),
        new SqlInt64Converter(),
        new SqlMoneyConverter(),
        new SqlSingleConverter(),
        new SqlStringConverter(),
        // TODO: converters for primitives from System.Data.SqlTypes that are classes not structs:
        // SqlBytes, SqlChars, SqlXml
        // Maybe SqlFileStream
    };
}

abstract class SqlPrimitiveConverterBase<T> : JsonConverter where T : struct, INullable, IComparable
{
    protected abstract object GetValue(T sqlValue);

    public override bool CanConvert(Type objectType)
    {
        return typeof(T) == objectType;
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        T sqlValue = (T)value;
        if (sqlValue.IsNull)
            writer.WriteNull();
        else
        {
            serializer.Serialize(writer, GetValue(sqlValue));
        }
    }
}

class SqlBinaryConverter : SqlPrimitiveConverterBase<SqlBinary>
{
    protected override object GetValue(SqlBinary sqlValue) { return sqlValue.Value; }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return SqlBinary.Null;
        return (SqlBinary)serializer.Deserialize<byte[]>(reader);
    }
}

class SqlBooleanConverter : SqlPrimitiveConverterBase<SqlBoolean>
{
    protected override object GetValue(SqlBoolean sqlValue) { return sqlValue.Value; }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return SqlBoolean.Null;
        return (SqlBoolean)serializer.Deserialize<bool>(reader);
    }
}

class SqlByteConverter : SqlPrimitiveConverterBase<SqlByte>
{
    protected override object GetValue(SqlByte sqlValue) { return sqlValue.Value; }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return SqlByte.Null;
        return (SqlByte)serializer.Deserialize<byte>(reader);
    }
}

class SqlDateTimeConverter : SqlPrimitiveConverterBase<SqlDateTime>
{
    protected override object GetValue(SqlDateTime sqlValue) { return sqlValue.Value; }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return SqlDateTime.Null;
        return (SqlDateTime)serializer.Deserialize<DateTime>(reader);
    }
}

class SqlDecimalConverter : SqlPrimitiveConverterBase<SqlDecimal>
{
    protected override object GetValue(SqlDecimal sqlValue) { return sqlValue.Value; }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return SqlDecimal.Null;
        return (SqlDecimal)serializer.Deserialize<decimal>(reader);
    }
}

class SqlDoubleConverter : SqlPrimitiveConverterBase<SqlDouble>
{
    protected override object GetValue(SqlDouble sqlValue) { return sqlValue.Value; }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return SqlDouble.Null;
        return (SqlDouble)serializer.Deserialize<double>(reader);
    }
}

class SqlGuidConverter : SqlPrimitiveConverterBase<SqlGuid>
{
    protected override object GetValue(SqlGuid sqlValue) { return sqlValue.Value; }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return SqlGuid.Null;
        return (SqlGuid)serializer.Deserialize<Guid>(reader);
    }
}

class SqlInt16Converter : SqlPrimitiveConverterBase<SqlInt16>
{
    protected override object GetValue(SqlInt16 sqlValue) { return sqlValue.Value; }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return SqlInt16.Null;
        return (SqlInt16)serializer.Deserialize<short>(reader);
    }
}

class SqlInt32Converter : SqlPrimitiveConverterBase<SqlInt32>
{
    protected override object GetValue(SqlInt32 sqlValue) { return sqlValue.Value; }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return SqlInt32.Null;
        return (SqlInt32)serializer.Deserialize<int>(reader);
    }
}

class SqlInt64Converter : SqlPrimitiveConverterBase<SqlInt64>
{
    protected override object GetValue(SqlInt64 sqlValue) { return sqlValue.Value; }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return SqlInt64.Null;
        return (SqlInt64)serializer.Deserialize<long>(reader);
    }
}

class SqlMoneyConverter : SqlPrimitiveConverterBase<SqlMoney>
{
    protected override object GetValue(SqlMoney sqlValue) { return sqlValue.Value; }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return SqlMoney.Null;
        return (SqlMoney)serializer.Deserialize<decimal>(reader);
    }
}

class SqlSingleConverter : SqlPrimitiveConverterBase<SqlSingle>
{
    protected override object GetValue(SqlSingle sqlValue) { return sqlValue.Value; }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return SqlSingle.Null;
        return (SqlSingle)serializer.Deserialize<float>(reader);
    }
}

class SqlStringConverter : SqlPrimitiveConverterBase<SqlString>
{
    protected override object GetValue(SqlString sqlValue) { return sqlValue.Value; }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return SqlString.Null;
        return (SqlString)serializer.Deserialize<string>(reader);
    }
}

工作.Net fiddle forked from your own。

如果您需要反序列化由此创建的 JSON，您还有两个问题。首先，SqlGeography such as Lat and Long 的一些属性是只读的。您将需要创建自定义 JsonConverter 以完全反序列化此类型。

其次，Json.NET 无法将行值的复杂对象 JSON 反序列化为未类型化的 DataTable。因此，如果您需要反序列化包含复杂对象的 JSON（例如您的序列化 SqlGeography），您有以下选择：

创建并反序列化为类型化的 DataTable。
直接使用 DataTableConverter 来使用预先分配的列填充预先存在的 DataTable，如 here 所示。

反序列化为 DTOs 列表，如下所示：

public class TableRowDTO
{
    [JsonConverter(typeof(SqlGeographyConverter))]
    public SqlGeography f1 { get; set; }
    public int id { get; set; }
}

根据需要，SqlGeographyConverter 是 SqlGeography 的自定义 JsonConverter。

然后做：

var settings = new JsonSerializerSettings().AddSqlConverters();
var list = JsonConvert.DeserializeObject<List<TableRowDTO>>(jsonString, settings);

Answer 2

实施 Json 转换器当然是解决无法在 Json.Net 中序列化 SqlGeography 的一种方法，但我认为更简单的解决方案是不直接序列化 SqlGeography。相反，创建一个包含来自 SqlGeography 的所有数据的自定义 class，然后 serialize/deserialize 代替。

public class SqlGeographyResult
    {
        private byte[] bytes { get; }

        public SqlGeographyResult(SqlGeography geography)
        {
            bytes = geography.Serialize().Value;
        }

        public SqlGeography ToGeography()
        {
            return SqlGeography.Deserialize(new System.Data.SqlTypes.SqlBytes(bytes));
        }
    }

Newtonsoft.Json.JsonSerializationException（从“System.Data.SqlTypes.SqlDouble”上的 'Value' 获取值时出错）序列化 SqlGeography

Newtonsoft.Json.JsonSerializationException (Error getting value from 'Value' on 'System.Data.SqlTypes.SqlDouble) serializing SqlGeography

c#

sql-server

json

geolocation

json.net