我尝试在数据库 SQL Server 2012 中使用 Newtonsoft.Json 版本“Newtonsoft.Json.10.0.3”将 DataTable
对象序列化为 Json。
该表有一个类型为“geography”的列,其中包含类型为 SqlGeography
的实例.
用于生成json的代码:
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”
我使用带有 SqlGeography 列的数据表创建了一个完整的 C# 程序(独立于 sql server 安装)来显示问题 Try it
我得到错误:
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)
我到达了 https://github.com/JamesNK/Newtonsoft.Json/issues/993 , 但它无济于事。
解决问题的任何帮助。
编辑:
根据@dbc的评论,我提供了生成json的完整源码。
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,并获得以下日志:
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'.
最佳答案
看起来像 System.Data.SqlTypes
中的 SqlDouble
之类的原始类型不能由 Json.NET 开箱即用地序列化,因为它们确实没有实现自己的 TypeConverter
。来自docs :
Primitive Types
.Net:
TypeConverter
(convertible to String)
JSON: String
这将有必要实现 custom JsonConverter
序列化这些类型。 Json.NET 有几个内置的 converters例如KeyValuePairConverter
对于内置的 .Net 类型,所以这并不罕见。
SqlBoolean
、SqlBinary
、SqlDouble
等除INullable
外不共享公共(public)基类或接口(interface)的事实需要一些看起来重复的代码:
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从你的 own fork 出来的.
如果您需要反序列化由此创建的 JSON,则会遇到另外两个问题。首先,SqlGeography
的一些属性例如Lat
和 Long
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 无法将包含行值的复杂对象的 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(例如序列化的 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
,如图所示 here .反序列化为
DTOs
的列表例如: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);
关于c# - Newtonsoft.Json.JsonSerializationException(从“System.Data.SqlTypes.SqlDouble”上的 'Value' 获取值时出错)序列化 SqlGeography,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/45848550/