I'm having an unusual problem. It might not be a very realistic scenario, but this is what I have gotten myself into, so please bear with me.
I have an API that returns Json and I'm using Json.NET to process the Json response. The problem is that the API can return a number of things and I have to be able to deserialize the response the following way:
The API can return a single Json object. In this case I have to deserialize it into an ExpandoObject and put it into a List<dynamic>.
The API can return null and undefined and the alike, in which case I have to return an empty list.
The API can return a single primitive value, like a Json string or a Json float. In this case I have to deserialize it into the appropriate .NET type, put it in a List<dynamic> and return that.
The API can return a Json array. In this case I have to deserialize the array into a List<dynamic>:
The elements in the array can be Json objects, in which case I have to deserialize them into ExpandoObject again, and put them in the list.
The elements can also be primitive values. In this case I have to deserialize them into the proper .NET type and put them in the list.
Based on my research, here's what I have come up so far:
protected IQueryable<dynamic> TestMethod(string r)
{
using (StringReader sr = new StringReader(r))
using (JsonTextReader reader = new JsonTextReader(sr))
{
if (!reader.Read())
{
return new List<ExpandoObject>().AsQueryable();
}
switch (reader.TokenType)
{
case JsonToken.None:
case JsonToken.Null:
case JsonToken.Undefined:
return new List<ExpandoObject>().AsQueryable();
case JsonToken.StartArray:
return JsonConvert.DeserializeObject<List<ExpandoObject>>(r).AsQueryable();
case JsonToken.StartObject:
return DeserializeAs<ExpandoObject>(r);
case JsonToken.Integer:
return DeserializeAs<long>(r);
case JsonToken.Float:
return DeserializeAs<double>(r);
// other Json primitives deserialized here
case JsonToken.StartConstructor:
// listing other not processed tokens
default:
throw new InvalidOperationException($"Token {reader.TokenType} cannot be the first token in the result");
}
}
}
private IQueryable<dynamic> DeserializeAs<T>(string r)
{
T instance = JsonConvert.DeserializeObject<T>(r);
return new List<dynamic>() { instance }.AsQueryable();
}
The problem is with the last bullet point. In the switch-case, when the deserializer encounters StartArray token, it tries to deserialize the json into a List<ExpandoObject>, but if the array contains integers, they cannot be deserialized into ExpandoObject.
Can anyone give me a simple solution to support both scenarios: array of Json objects to List<ExpandoObject> and array of Json primitives to their respective list?
Since Json.NET is licensed under the MIT license, you could adapt the logic of ExpandoObjectConverter to fit your needs, and create the following method:
public static class JsonExtensions
{
public static IQueryable<object> ReadJsonAsDynamicQueryable(string json, JsonSerializerSettings settings = null)
{
var serializer = JsonSerializer.CreateDefault(settings);
using (StringReader sr = new StringReader(json))
using (JsonTextReader reader = new JsonTextReader(sr))
{
var root = JsonExtensions.ReadJsonAsDynamicQueryable(reader, serializer);
return root;
}
}
public static IQueryable<dynamic> ReadJsonAsDynamicQueryable(JsonReader reader, JsonSerializer serializer)
{
dynamic obj;
if (!TryReadJsonAsDynamic(reader, serializer, out obj) || obj == null)
return Enumerable.Empty<dynamic>().AsQueryable();
var list = obj as IList<dynamic> ?? new [] { obj };
return list.AsQueryable();
}
public static bool TryReadJsonAsDynamic(JsonReader reader, JsonSerializer serializer, out dynamic obj)
{
// Adapted from:
// https://github.com/JamesNK/Newtonsoft.Json/blob/master/Src/Newtonsoft.Json/Converters/ExpandoObjectConverter.cs
// License:
// https://github.com/JamesNK/Newtonsoft.Json/blob/master/LICENSE.md
if (reader.TokenType == JsonToken.None)
if (!reader.Read())
{
obj = null;
return false;
}
switch (reader.TokenType)
{
case JsonToken.StartArray:
var list = new List<dynamic>();
ReadList(reader,
(r) =>
{
dynamic item;
if (TryReadJsonAsDynamic(reader, serializer, out item))
list.Add(item);
});
obj = list;
return true;
case JsonToken.StartObject:
obj = serializer.Deserialize<ExpandoObject>(reader);
return true;
default:
if (reader.TokenType.IsPrimitiveToken())
{
obj = reader.Value;
return true;
}
else
{
throw new JsonSerializationException("Unknown token: " + reader.TokenType);
}
}
}
static void ReadList(this JsonReader reader, Action<JsonReader> readValue)
{
while (reader.Read())
{
switch (reader.TokenType)
{
case JsonToken.Comment:
break;
default:
readValue(reader);
break;
case JsonToken.EndArray:
return;
}
}
throw new JsonSerializationException("Unexpected end when reading List.");
}
public static bool IsPrimitiveToken(this JsonToken token)
{
switch (token)
{
case JsonToken.Integer:
case JsonToken.Float:
case JsonToken.String:
case JsonToken.Boolean:
case JsonToken.Undefined:
case JsonToken.Null:
case JsonToken.Date:
case JsonToken.Bytes:
return true;
default:
return false;
}
}
}
Then use it like:
protected IQueryable<dynamic> TestMethod(string r)
{
return JsonExtensions.ReadJsonAsDynamicQueryable(r);
}
Or, you could call ReadJsonAsDynamicQueryable from within the ReadJson() method of a custom JsonConverter that you create.
Sample fiddle.
Related
I have a asp.net core method, I want it to accept RAW json, I do not and will not always know the schema of the json object, so I am using dynamic types with dot notation.
This method works when I string the json escaping each character. I have tried to use the json body directly, but this did not work. So it seems my option were to Serialize and then Deserialize the json. ( very redundant) but it seems to throw error any other way if I try to use the JSON body directly.
In the debugger, everything seems to work with the Serialize and Deserialize of the object / string, but throws an error on the id(property) when I try to cast the object to string and gives the error. (In the debugger I am able to see the Id correctly though).
({Microsoft.CSharp.RuntimeBinder.RuntimeBinderException: Cannot convert type 'System.Text.Json.JsonElement' to 'string')}
I really do not see why it gives the type as a string yet cannot convert it. I have even tried to remove the casting, and still receive this error.
public IActionResult Post([FromBody] ExpandoObject requestInput)
{
try
{
//Makes a JSON String
var stringObject = (string) JsonSerializer.Serialize(requestInput);
DateTime time = DateTime.UtcNow;
// Recreated the Json Object
dynamic requestObject = JsonSerializer.Deserialize<ExpandoObject>(stringObject);
// Throws Error here, yet it shows Value as the correct Id number (Value: Type String)
string reqObject = (string) requestObject.Id;
So there is no support for ExpandoObject in .NET Core, yet. MS says that maybe it will be added in .NET 5.0. Until then, you can use this JsonConverter I found on a thread. I will post the code here in case that thread goes away.
You can use it like this:
[HttpPost, Route("testPost")]
public IActionResult TestPost([FromBody] object obj) // just use "object"
{
// object is: { "hello":"world" }
var myDynamic = JsonSerializer.Deserialize<dynamic>(
JsonSerializer.Serialize(obj), new JsonSerializerOptions
{
Converters = { new DynamicJsonConverter() }
});
var test = (string)myDynamic.hello;
// test will equal "world"
return Ok();
}
Here is the converter:
/// <summary>
/// Temp Dynamic Converter
/// by:tchivs#live.cn
/// </summary>
public class DynamicJsonConverter : JsonConverter<dynamic>
{
public override dynamic Read(ref Utf8JsonReader reader,
Type typeToConvert,
JsonSerializerOptions options)
{
if (reader.TokenType == JsonTokenType.True)
{
return true;
}
if (reader.TokenType == JsonTokenType.False)
{
return false;
}
if (reader.TokenType == JsonTokenType.Number)
{
if (reader.TryGetInt64(out long l))
{
return l;
}
return reader.GetDouble();
}
if (reader.TokenType == JsonTokenType.String)
{
if (reader.TryGetDateTime(out DateTime datetime))
{
return datetime;
}
return reader.GetString();
}
if (reader.TokenType == JsonTokenType.StartObject)
{
using JsonDocument documentV = JsonDocument.ParseValue(ref reader);
return ReadObject(documentV.RootElement);
}
// Use JsonElement as fallback.
// Newtonsoft uses JArray or JObject.
JsonDocument document = JsonDocument.ParseValue(ref reader);
return document.RootElement.Clone();
}
private object ReadObject(JsonElement jsonElement)
{
IDictionary<string, object> expandoObject = new ExpandoObject();
foreach (var obj in jsonElement.EnumerateObject())
{
var k = obj.Name;
var value = ReadValue(obj.Value);
expandoObject[k] = value;
}
return expandoObject;
}
private object? ReadValue(JsonElement jsonElement)
{
object? result = null;
switch (jsonElement.ValueKind)
{
case JsonValueKind.Object:
result = ReadObject(jsonElement);
break;
case JsonValueKind.Array:
result = ReadList(jsonElement);
break;
case JsonValueKind.String:
//TODO: Missing Datetime&Bytes Convert
result = jsonElement.GetString();
break;
case JsonValueKind.Number:
//TODO: more num type
result = 0;
if (jsonElement.TryGetInt64(out long l))
{
result = l;
}
break;
case JsonValueKind.True:
result = true;
break;
case JsonValueKind.False:
result = false;
break;
case JsonValueKind.Undefined:
case JsonValueKind.Null:
result = null;
break;
default:
throw new ArgumentOutOfRangeException();
}
return result;
}
private object? ReadList(JsonElement jsonElement)
{
IList<object?> list = new List<object?>();
foreach (var item in jsonElement.EnumerateArray())
{
list.Add(ReadValue(item));
}
return list.Count == 0 ? null : list;
}
public override void Write(Utf8JsonWriter writer,
object value,
JsonSerializerOptions options)
{
// writer.WriteStringValue(value.ToString());
}
}
Edited To Add:
Here is a much slicker way to handle dynamic using the converter above as pointed out by Aluan in the comments. In your Startup.cs class, add this:
services.AddControllers().AddJsonOptions(options =>
options.JsonSerializerOptions.Converters.Add(new DynamicJsonConverter()));
Then you don't have to do any goofy stuff in your controller. You can just set the body parameter as dynamic and it magically works:
[HttpPost, Route("testPost")]
public IActionResult TestPost([FromBody] dynamic obj)
{
// object is: { "hello":"world" }
var test = (string)obj.hello;
// test will equal "world"
return Ok();
}
Way nicer!
How can one deserialize the following JSON
{
"result" : {
"master" : [
["one", "two"],
["three", "four"],
["five", "six", "seven"],
],
"blaster" : [
["ein", "zwei"],
["drei", "vier"]
],
"surprise" : "nonsense-nonsense-nonsense"
}
}
into the following data structure
class ResultView
{
public Dictionary<string, string[][]> Result { get; set; }
}
with Json.NET?
It has to be dictionary because key names such as 'master' and 'blaster' are unknown at the time of compilation. What is known is that they always point to an array of arrays of strings. The problem is that key 'surprise', whose name is known and always the same, points to something that cannot be interpreted as string[][], and this leads to exception in Json.NET.
Is there any way to make Json.NET ignore specific dictionary key?
You can introduce a custom generic JsonConverter for IDictionary<string, TValue> that filters out invalid dictionary values (i.e. those that cannot be deserialized successfully to the dictionary value type):
public class TolerantDictionaryItemConverter<TDictionary, TValue> : JsonConverter where TDictionary : IDictionary<string, TValue>
{
public override bool CanConvert(Type objectType)
{
return typeof(TDictionary).IsAssignableFrom(objectType);
}
public override object ReadJson(JsonReader reader, Type dictionaryType, object existingValue, JsonSerializer serializer)
{
// Get contract information
var contract = serializer.ContractResolver.ResolveContract(dictionaryType) as JsonDictionaryContract;
if (contract == null)
throw new JsonSerializationException(string.Format("Invalid JsonDictionaryContract for {0}", dictionaryType));
if (contract.DictionaryKeyType != typeof(string))
throw new JsonSerializationException(string.Format("Key type {0} not supported", dictionaryType));
var itemContract = serializer.ContractResolver.ResolveContract(contract.DictionaryValueType);
// Process the first token
var tokenType = reader.SkipComments().TokenType;
if (tokenType == JsonToken.Null)
return null;
if (reader.TokenType != JsonToken.StartObject)
throw new JsonSerializationException(string.Format("Expected {0}, encountered {1} at path {2}", JsonToken.StartArray, reader.TokenType, reader.Path));
// Allocate the dictionary
var dictionary = existingValue as IDictionary<string, TValue> ?? (IDictionary<string, TValue>) contract.DefaultCreator();
// Process the collection items
while (reader.Read())
{
if (reader.TokenType == JsonToken.EndObject)
{
return dictionary;
}
else if (reader.TokenType == JsonToken.PropertyName)
{
var key = (string)reader.Value;
reader.ReadSkipCommentsAndAssert();
// For performance, skip tokens we can easily determine cannot be deserialized to itemContract
if (itemContract.QuickRejectStartToken(reader.TokenType))
{
System.Diagnostics.Debug.WriteLine(string.Format("value for {0} skipped", key));
reader.Skip();
}
else
{
// What we want to do is to distinguish between JSON files that are not WELL-FORMED
// (e.g. truncated) and that are not VALID (cannot be deserialized to the current item type).
// An exception must still be thrown for an ill-formed file.
// Thus we first load into a JToken, then deserialize.
var token = JToken.Load(reader);
try
{
var value = serializer.Deserialize<TValue>(token.CreateReader());
dictionary.Add(key, value);
}
catch (Exception)
{
System.Diagnostics.Debug.WriteLine(string.Format("value for {0} skipped", key));
}
}
}
else if (reader.TokenType == JsonToken.Comment)
{
continue;
}
else
{
throw new JsonSerializationException(string.Format("Unexpected token type {0} object at path {1}.", reader.TokenType, reader.Path));
}
}
// Should not come here.
throw new JsonSerializationException("Unclosed object at path: " + reader.Path);
}
public override bool CanWrite { get { return false; } }
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
throw new NotImplementedException();
}
}
public static partial class JsonExtensions
{
public static JsonReader SkipComments(this JsonReader reader)
{
while (reader.TokenType == JsonToken.Comment && reader.Read())
;
return reader;
}
public static void ReadSkipCommentsAndAssert(this JsonReader reader)
{
if (reader == null)
throw new ArgumentNullException();
while (reader.Read())
{
if (reader.TokenType != JsonToken.Comment)
return;
}
new JsonReaderException(string.Format("Unexpected end at path {0}", reader.Path));
}
internal static bool QuickRejectStartToken(this JsonContract contract, JsonToken token)
{
if (contract is JsonLinqContract)
return false;
switch (token)
{
case JsonToken.None:
return true;
case JsonToken.StartObject:
return !(contract is JsonContainerContract) || contract is JsonArrayContract; // reject if not dictionary or object
case JsonToken.StartArray:
return !(contract is JsonArrayContract); // reject if not array
case JsonToken.Null:
return contract.CreatedType.IsValueType && Nullable.GetUnderlyingType(contract.UnderlyingType) == null;
// Primitives
case JsonToken.Integer:
case JsonToken.Float:
case JsonToken.String:
case JsonToken.Boolean:
case JsonToken.Undefined:
case JsonToken.Date:
case JsonToken.Bytes:
return !(contract is JsonPrimitiveContract); // reject if not primitive.
default:
return false;
}
}
}
Then you can add it to settings as follows:
var settings = new JsonSerializerSettings
{
Converters = { new TolerantDictionaryItemConverter<IDictionary<string, TValue>, TValue>() },
};
var root = JsonConvert.DeserializeObject<ResultView>(json, settings);
Or add it directly to ResultView with JsonConverterAttribute:
class ResultView
{
[JsonConverter(typeof(TolerantDictionaryItemConverter<IDictionary<string, string[][]>, string[][]>))]
public Dictionary<string, string[][]> Result { get; set; }
}
Notes:
I wrote the converter in a general way to handle any type of dictionary value including primitives such as int or DateTime as well as arrays or objects.
While a JSON file with invalid dictionary values (ones that cannot be deserialized to the dictionary value type) should be deserializable, an ill-formed JSON file (e.g. one that is truncated) should still result in an exception being thrown.
The converter handles this by first loading the value into a JToken then attempting to deserialize the token. If the file is ill-formed, JToken.Load(reader) will throw an exception, which is intentionally not caught.
Json.NET's exception handling is reported to be "very flaky" (see e.g. Issue #1580: Regression from Json.NET v6: cannot skip an invalid object value type in an array via exception handling) so I did not rely on it to skip invalid dictionary values.
I'm not 100% sure I got all cases of comment handling correct. So that may need additional testing.
Working sample .Net fiddle here.
I think you could ignore exceptions like this:
ResultView result = JsonConvert.DeserializeObject<ResultView>(jsonString,
new JsonSerializerSettings
{
Error = delegate (object sender, Newtonsoft.Json.Serialization.ErrorEventArgs args)
{
// System.Diagnostics.Debug.WriteLine(args.ErrorContext.Error.Message);
args.ErrorContext.Handled = true;
}
}
);
args.ErrorContext.Error.Message would contain the actual error message.
args.ErrorContext.Handled = true; will tell Json.Net to proceed.
How can I get Json.NET to deserialize into dynamic objects but still do reference resolution?
dynamic d=JsonConvert.DeserializeObject<ExpandoObject>(...) just as
dynamic d=JsonConvert.DeserializeObject(...) returns a dynamic object but they don't resolve the $ref and $id parts. (An ExpandoObject eo for example will only have eo["$ref"]="..." and doesn't have the properties it should have because it's not the same as the $id-Object)
What I've found out is that I need the contract resolver resolve to a dynamic contract - which ExpandoObject only does if I explicitly tell Json.NET with a custom ContractResolver.
Still It seems the ExpandoObject is parsed with it's own Converter and it fails again.
I've tried a custom class inheriting from IDynamicMetaObjectProvider which resulted in an infinite loop and didn't seem like the right thing. I would actually expect some easy solution to get ExpandoObject to have reference resolution.
Any help?
Since Json.NET is open source and its MIT license allows modification, the easiest solution may be to adapt its ExpandoObjectConverter to your needs:
/// <summary>
/// Converts an ExpandoObject to and from JSON, handling object references.
/// </summary>
public class ObjectReferenceExpandoObjectConverter : JsonConverter
{
// Adapted from https://github.com/JamesNK/Newtonsoft.Json/blob/master/Src/Newtonsoft.Json/Converters/ExpandoObjectConverter.cs
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
// can write is set to false
throw new NotImplementedException();
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
return ReadValue(serializer, reader);
}
private object ReadValue(JsonSerializer serializer, JsonReader reader)
{
while (reader.TokenType == JsonToken.Comment)
{
if (!reader.Read())
throw reader.CreateException("Unexpected end when reading ExpandoObject.");
}
switch (reader.TokenType)
{
case JsonToken.StartObject:
return ReadObject(serializer, reader);
case JsonToken.StartArray:
return ReadList(serializer, reader);
default:
if (JsonTokenUtils.IsPrimitiveToken(reader.TokenType))
return reader.Value;
throw reader.CreateException("Unexpected token when converting ExpandoObject");
}
}
private object ReadList(JsonSerializer serializer, JsonReader reader)
{
IList<object> list = new List<object>();
while (reader.Read())
{
switch (reader.TokenType)
{
case JsonToken.Comment:
break;
default:
object v = ReadValue(serializer, reader);
list.Add(v);
break;
case JsonToken.EndArray:
return list;
}
}
throw reader.CreateException("Unexpected end when reading ExpandoObject.");
}
private object ReadObject(JsonSerializer serializer, JsonReader reader)
{
IDictionary<string, object> expandoObject = null;
object referenceObject = null;
while (reader.Read())
{
switch (reader.TokenType)
{
case JsonToken.PropertyName:
string propertyName = reader.Value.ToString();
if (!reader.Read())
throw new InvalidOperationException("Unexpected end when reading ExpandoObject.");
object v = ReadValue(serializer, reader);
if (propertyName == "$ref")
{
var id = (v == null ? null : Convert.ToString(v, CultureInfo.InvariantCulture));
referenceObject = serializer.ReferenceResolver.ResolveReference(serializer, id);
}
else if (propertyName == "$id")
{
var id = (v == null ? null : Convert.ToString(v, CultureInfo.InvariantCulture));
serializer.ReferenceResolver.AddReference(serializer, id, (expandoObject ?? (expandoObject = new ExpandoObject())));
}
else
{
(expandoObject ?? (expandoObject = new ExpandoObject()))[propertyName] = v;
}
break;
case JsonToken.Comment:
break;
case JsonToken.EndObject:
if (referenceObject != null && expandoObject != null)
throw reader.CreateException("ExpandoObject contained both $ref and real data");
return referenceObject ?? expandoObject;
}
}
throw reader.CreateException("Unexpected end when reading ExpandoObject.");
}
public override bool CanConvert(Type objectType)
{
return (objectType == typeof(ExpandoObject));
}
public override bool CanWrite
{
get { return false; }
}
}
public static class JsonTokenUtils
{
// Adapted from https://github.com/JamesNK/Newtonsoft.Json/blob/master/Src/Newtonsoft.Json/Utilities/JsonTokenUtils.cs
public static bool IsPrimitiveToken(this JsonToken token)
{
switch (token)
{
case JsonToken.Integer:
case JsonToken.Float:
case JsonToken.String:
case JsonToken.Boolean:
case JsonToken.Undefined:
case JsonToken.Null:
case JsonToken.Date:
case JsonToken.Bytes:
return true;
default:
return false;
}
}
}
public static class JsonReaderExtensions
{
public static JsonSerializationException CreateException(this JsonReader reader, string format, params object[] args)
{
// Adapted from https://github.com/JamesNK/Newtonsoft.Json/blob/master/Src/Newtonsoft.Json/JsonPosition.cs
var lineInfo = reader as IJsonLineInfo;
var path = (reader == null ? null : reader.Path);
var message = string.Format(CultureInfo.InvariantCulture, format, args);
if (!message.EndsWith(Environment.NewLine, StringComparison.Ordinal))
{
message = message.Trim();
if (!message.EndsWith(".", StringComparison.Ordinal))
message += ".";
message += " ";
}
message += string.Format(CultureInfo.InvariantCulture, "Path '{0}'", path);
if (lineInfo != null && lineInfo.HasLineInfo())
message += string.Format(CultureInfo.InvariantCulture, ", line {0}, position {1}", lineInfo.LineNumber, lineInfo.LinePosition);
message += ".";
return new JsonSerializationException(message);
}
}
And then use it like:
var settings = new JsonSerializerSettings { PreserveReferencesHandling = PreserveReferencesHandling.Objects, ReferenceLoopHandling = ReferenceLoopHandling.Serialize };
settings.Converters.Add(new ObjectReferenceExpandoObjectConverter());
dynamic d = JsonConvert.DeserializeObject<ExpandoObject>(json, settings);
The way I did it now is with a postprocessing step and a recursive function that's doing its own reference saving and rewiring:
private static void Reffing(this IDictionary<string, object> current, Action<object> exchange,IDictionary<string, object> refdic)
{
object value;
if(current.TryGetValue("$ref", out value))
{
if(!refdic.TryGetValue((string) value, out value))
throw new Exception("ref not found ");
if (exchange != null)
exchange(value);
return;
}
if (current.TryGetValue("$id", out value))
{
refdic[(string) value] = current;
}
foreach (var kvp in current.ToList())
{
if (kvp.Key.StartsWith("$"))
continue;
var expandoObject = kvp.Value as ExpandoObject;
if(expandoObject != null)
Reffing(expandoObject,o => current[kvp.Key]=o,refdic);
var list = kvp.Value as IList<object>;
if (list == null) continue;
for (var i = 0; i < list.Count; i++)
{
var lEO = list[i] as ExpandoObject;
if(lEO!=null)
Reffing(lEO,o => list[i]=o,refdic);
}
}
}
used as:
var test = JsonConvert.DeserializeObject<ExpandoObject>(...);
var dictionary = new Dictionary<string, object>();
Reffing(test,null,dictionary);
I currently have a list builder from a separate class:
public class psuedoMe {
public string relName { get; set; }
public List<string> lstName { get; set; }
}
I have a function that populates this, but then writes it to Json using Newtonsoft.Json.JsonWriter:
private static string returnJson(List<psuedoMe> sentList)
{
StringBuilder jsonSB = new StringBuilder();
StringWriter jsonSW = new StringWriter(jsonSB);
using (JsonWriter jsonWrite = new JsonTextWriter(jsonSW))
{
jsonWrite.WriteStartArray();
foreach (psuedoMe sentItem in sentList)
{
jsonWrite.WriteStartObject();
foreach (System.Reflection.PropertyInfo propInfo in sentItem.GetType().GetProperties())
{
jsonWrite.WritePropertyName(propInfo.Name);
jsonWrite.WriteValue(propInfo.GetValue(sentItem, null));
}
jsonWrite.WriteEndObject();
}
jsonWrite.WriteEndArray();
}
return jsonSB.ToString();
}
However I am receiving an error when it tries to write the public List<string> lstName into jsonSB. I've tried excluding only the lstName from the JsonWriter however this only then loops through the list and doesn't write it to the jsonSB at the end.
Is there anyway of using the above returnJson to write to the list of strings?
There error I get is: Newtonsoft.Json.JsonWriterException: Unsupported type: System.Collections.Generic.List1[System.String].
Which version of JSON.NET you're using? Here's the source code of JsonWriter class's WriteValue method
public virtual void WriteValue(object value)
{
if (value == null)
{
WriteNull();
return;
}
else if (value is IConvertible)
{
IConvertible convertible = value as IConvertible;
switch (convertible.GetTypeCode())
{
case TypeCode.String:
WriteValue(convertible.ToString(CultureInfo.InvariantCulture));
return;
case TypeCode.Char:
WriteValue(convertible.ToChar(CultureInfo.InvariantCulture));
return;
case TypeCode.Boolean:
WriteValue(convertible.ToBoolean(CultureInfo.InvariantCulture));
return;
case TypeCode.SByte:
WriteValue(convertible.ToSByte(CultureInfo.InvariantCulture));
return;
case TypeCode.Int16:
WriteValue(convertible.ToInt16(CultureInfo.InvariantCulture));
return;
case TypeCode.UInt16:
WriteValue(convertible.ToUInt16(CultureInfo.InvariantCulture));
return;
case TypeCode.Int32:
WriteValue(convertible.ToInt32(CultureInfo.InvariantCulture));
return;
case TypeCode.Byte:
WriteValue(convertible.ToByte(CultureInfo.InvariantCulture));
return;
case TypeCode.UInt32:
WriteValue(convertible.ToUInt32(CultureInfo.InvariantCulture));
return;
case TypeCode.Int64:
WriteValue(convertible.ToInt64(CultureInfo.InvariantCulture));
return;
case TypeCode.UInt64:
WriteValue(convertible.ToUInt64(CultureInfo.InvariantCulture));
return;
case TypeCode.Single:
WriteValue(convertible.ToSingle(CultureInfo.InvariantCulture));
return;
case TypeCode.Double:
WriteValue(convertible.ToDouble(CultureInfo.InvariantCulture));
return;
case TypeCode.DateTime:
WriteValue(convertible.ToDateTime(CultureInfo.InvariantCulture));
return;
case TypeCode.Decimal:
WriteValue(convertible.ToDecimal(CultureInfo.InvariantCulture));
return;
case TypeCode.DBNull:
WriteNull();
return;
}
}
#if !PocketPC && !NET20
else if (value is DateTimeOffset)
{
WriteValue((DateTimeOffset)value);
return;
}
#endif
else if (value is byte[])
{
WriteValue((byte[])value);
return;
}
throw new ArgumentException("Unsupported type: {0}. Use the JsonSerializer class to get the object's JSON representation.".FormatWith(CultureInfo.InvariantCulture, value.GetType()));
}
As you can see, it doesn't have support for List<T>. So for List<T> it will throw Unsupported type exception, and even in exception message it is suggesting to use JsonSerializer to get object's JSON representation.
This question already has answers here:
How do I use JSON.NET to deserialize into nested/recursive Dictionary and List?
(5 answers)
Closed 7 years ago.
I'm trying to convert some older work to use Newtonsoft JSON.NET. The default handling using the System.Web.Script.Serialization.JavaScriptSerializer.Deserialize method (e.g. if no target type is specified) is to return a Dictionary<string,object> for inner objects.
This is actually a really useful basic type for JSON since it also happens to be the underlying type used by ExpandoObjects and is the most sensible internal implementation for dynamic types.
If I specify this type, e.g.:
var dict = JsonConvert.DeserializeObject<Dictionary<string,object>>(json);
JSON.NET will deserialize the outermost object structure correctly, but it returns a JObject type for any inner structures. What I really need is for the same outer structure to be used for any inner object-type structures.
Is there a way to specify a type to be used for inner objects, and not just the outermost type returned?
In order to get Json.Net to deserialize a json string into an IDictionary<string, object> including deserializing nested objects and arrays you will need to create a custom class that derives from the JsonConverter abstract class provided by Json.Net.
It is in your derived JsonConverter where you put the implementation of how an object should be written to and from json.
You can use your custom JsonConverter like this:
var o = JsonConvert.DeserializeObject<IDictionary<string, object>>(json, new DictionaryConverter());
Here is a custom JsonConverter I have used with success in the past to achieve the same goals as you outline in your question:
public class DictionaryConverter : JsonConverter {
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) { this.WriteValue(writer, value); }
private void WriteValue(JsonWriter writer, object value) {
var t = JToken.FromObject(value);
switch (t.Type) {
case JTokenType.Object:
this.WriteObject(writer, value);
break;
case JTokenType.Array:
this.WriteArray(writer, value);
break;
default:
writer.WriteValue(value);
break;
}
}
private void WriteObject(JsonWriter writer, object value) {
writer.WriteStartObject();
var obj = value as IDictionary<string, object>;
foreach (var kvp in obj) {
writer.WritePropertyName(kvp.Key);
this.WriteValue(writer, kvp.Value);
}
writer.WriteEndObject();
}
private void WriteArray(JsonWriter writer, object value) {
writer.WriteStartArray();
var array = value as IEnumerable<object>;
foreach (var o in array) {
this.WriteValue(writer, o);
}
writer.WriteEndArray();
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) {
return ReadValue(reader);
}
private object ReadValue(JsonReader reader) {
while (reader.TokenType == JsonToken.Comment) {
if (!reader.Read()) throw new JsonSerializationException("Unexpected Token when converting IDictionary<string, object>");
}
switch (reader.TokenType) {
case JsonToken.StartObject:
return ReadObject(reader);
case JsonToken.StartArray:
return this.ReadArray(reader);
case JsonToken.Integer:
case JsonToken.Float:
case JsonToken.String:
case JsonToken.Boolean:
case JsonToken.Undefined:
case JsonToken.Null:
case JsonToken.Date:
case JsonToken.Bytes:
return reader.Value;
default:
throw new JsonSerializationException
(string.Format("Unexpected token when converting IDictionary<string, object>: {0}", reader.TokenType));
}
}
private object ReadArray(JsonReader reader) {
IList<object> list = new List<object>();
while (reader.Read()) {
switch (reader.TokenType) {
case JsonToken.Comment:
break;
default:
var v = ReadValue(reader);
list.Add(v);
break;
case JsonToken.EndArray:
return list;
}
}
throw new JsonSerializationException("Unexpected end when reading IDictionary<string, object>");
}
private object ReadObject(JsonReader reader) {
var obj = new Dictionary<string, object>();
while (reader.Read()) {
switch (reader.TokenType) {
case JsonToken.PropertyName:
var propertyName = reader.Value.ToString();
if (!reader.Read()) {
throw new JsonSerializationException("Unexpected end when reading IDictionary<string, object>");
}
var v = ReadValue(reader);
obj[propertyName] = v;
break;
case JsonToken.Comment:
break;
case JsonToken.EndObject:
return obj;
}
}
throw new JsonSerializationException("Unexpected end when reading IDictionary<string, object>");
}
public override bool CanConvert(Type objectType) { return typeof(IDictionary<string, object>).IsAssignableFrom(objectType); }
}
When Deserializing your complex objects using Json, you need to add a JsonSerializer Settings as a parameter. This will ensure that all of the inner types get deserialized properly.
private JsonSerializerSettings _jsonSettings = new JsonSerializerSettings
{
TypeNameHandling = TypeNameHandling.All,
TypeNameAssemblyFormat = FormatterAssemblyStyle.Full
};
When Serializing your object, you can use the SerializerSettings:
string json= JsonConvert.SerializeObject(myObject, _jsonSettings)
Then when you are deserializing, use:
var dict = JsonConvert.DeserializeObject<Dictionary<string, object>>(json, _jsonSettings);
Also, when you serialize, add the JsonSerializerSettings to your SerializeObject(object, settings)
Edit: You can also change the TypeNameHandling and TypeNameAssemblyFormat if you need to. I have them set at 'All' and 'Full' respectively to ensure that my complex objects get serialized and deserialized properly without doubt, but intellisense provides you with other alternatives