Deserialize json with C# .NET Core

Question

Im trying to deserialize data that Ive got over POST in JSON format but having some problem.

The error message is:

SerializationException: Expecting state 'Element'.. Encountered 'Text' with name '', namespace ''. System.Runtime.Serialization.XmlObjectSerializerReadContext.HandleMemberNotFound(XmlReaderDelegator xmlReader, ExtensionDataObject extensionData, int memberIndex)

Controller where the serialization is happening:

    public String RequestToken(string userData)
    {
            Contract.Ensures(Contract.Result<string>() != null);
            UserModel deserializedUser = new UserModel();
            MemoryStream ms = new MemoryStream(Encoding.UTF8.GetBytes(userData));
            ms.Position = 0;
            DataContractJsonSerializer ser = new DataContractJsonSerializer(deserializedUser.GetType());
            deserializedUser = ser.ReadObject(ms) as UserModel;
    }

UserModel that is used as a contract:

using System;
using System.Runtime.Serialization;
using MongoDB.Bson;
using MongoDB.Bson.Serialization.Attributes;

namespace WishareIntegrationApi.Entities
{
    [DataContract]
    public class UserModel
    {
        [BsonId]
        [BsonRepresentation(BsonType.String)]
        [DataMember]
        public ObjectId _id { get; set; }
        [DataMember]
        public string displayName { get; set; }
        [DataMember]
        public string photoURL { get; set; }
        [DataMember]
        public string email { get; set; }
        [DataMember]
        public int registeredAt { get; set; }
    }
}

And an example JSON i'm sending over post:

{"_id":"8kmXH1fzSrVS8PqNLMwyhRH4hBw1","displayName":"Michal Takáč","photoURL":"https://lh3.googleusercontent.com/-xa5oE48RffQ/AAAAAAAAAAI/AAAAAAAACDE/OLrtV5-VIvw/photo.jpg","email":"[email protected]"}

"System.Runtime.Serialization.Xml"... in the error. Hmm. Check your default serializer. — ADyson
– ADyson, Commented Jan 3, 2018 at 10:23
Why are you using the deprecated DataContractJsonSerializer? .NET itself uses JSON.NET in ASP.NET Web API. .NET Core uses Json.NET both in both in ASP.NET MVC and Web API. By using DataContractJsonSerializer you are introducing a dependency on a legacy class — Panagiotis Kanavos
– Panagiotis Kanavos, Commented Jan 3, 2018 at 10:25
I also noticed this one, but im totally new to .NET. Can you elaborate on that default serializer thingy? — Michal Takáč
– Michal Takáč, Commented Jan 3, 2018 at 10:26
@MichalTakáč forget about default serializers and use JSON.NET. A simple JSonConvert.DeserializeObject<UserModel>(userData)` is enough — Panagiotis Kanavos
– Panagiotis Kanavos, Commented Jan 3, 2018 at 10:27
I just switched to JSON.NET and it works well. Thank you for help :) — Michal Takáč
– Michal Takáč, Commented Jan 3, 2018 at 10:32

Alexei Levenkov · Accepted Answer · 2018-12-26 22:07:43Z

15

Switch to JSON.Net.

JSON serialization APIs are not part of .Net core and I don't expect them to port that over. If you used classes from namespaces like System.Web.Script.Serialization switch to other serialization, in particular Microsfot frameworks based on .Net core use JSON.Net serializers.

As mentioned by many users in comments, I've switched from old way of doing serialization/deserialization using contracts to JSON.NET

Here is the correct solution for the controller

public async Task<String> RequestToken(string userData)
{
     var user = JsonConvert.DeserializeObject<UserModel>(userData);
}

edited Dec 26, 2018 at 22:07

Alexei Levenkov

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answered Jan 3, 2018 at 11:13

Michal Takáč

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2 Comments

Mauricio Gracia Gutierrez Over a year ago

$ dotnet add package Microsoft.AspNetCore.Mvc.NewtonsoftJson

NetMage Over a year ago

But they have replaced them now with System.Text.Json since .Net Core 3.1.

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