Converting JSON object to Data.Entities.Models.MyModel

问题

So,

I'm having an issue with serializing my JSON object to my Entity/Model object.

I have the following code snippet:

var serializedValue = JsonConvert.SerializeObject(newRows, new MyModelConverter());

var csvToSave = JsonConvert.DeserializeObject<MyModel>(serializedValue);

Where newRows is a List<KeyValuePair<string,string>>

Where Entity looks something like this:

public class MyModel: Entity
{
    public int Id { get; set; } //primary key

    public DateTime TouchTime { get; set; }

    public DateTime InstallTime { get; set; }

    public string EventName { get; set; }

}

Looking back at old StackOverflow posts, I see I need to use a custom JsonConverter so that I can get my data to be converted to a json object.

Here's my converter class:

public class MyModelConverter : JsonCreationConverter<MyModel>
{
    protected override MyModel Create(Type objectType, JObject jObject)
    {
        return new MyModel();
    }
}

public abstract class JsonCreationConverter<T> : JsonConverter
{
    /// <summary>
    /// Create an instance of objectType, based properties in the JSON object
    /// </summary>
    /// <param name="objectType">type of object expected</param>
    /// <param name="jObject">
    /// contents of JSON object that will be deserialized
    /// </param>
    /// <returns></returns>
    protected abstract T Create(Type objectType, JObject jObject);

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

    public override object ReadJson(JsonReader reader,
                                    Type objectType,
                                     object existingValue,
                                     JsonSerializer serializer)
    {
        // Load JObject from stream
        JObject jObject = JObject.Load(reader);

        // Create target object based on JObject
        T target = Create(objectType, jObject);

        // Populate the object properties
        serializer.Populate(jObject.CreateReader(), target);

        return target;
    }

    public override void WriteJson(JsonWriter writer,
                                   object value,
                                   JsonSerializer serializer)
    {
        List<KeyValuePair<string, object>> list = value as List<KeyValuePair<string, object>>;
        writer.WriteStartArray();
        foreach (var item in list)
        {
            writer.WriteStartObject();
            writer.WritePropertyName(item.Key);
            writer.WriteValue(item.Value);
            writer.WriteEndObject();
        }
        writer.WriteEndArray();
    }
}

But when I run my program, I get this error instead:

Cannot deserialize the current JSON array (e.g. [1,2,3]) into type 'Data.Entities.Models.MyModel' because the type requires a JSON object (e.g. {"name":"value"}) to deserialize correctly.

Where my Json object looks like this now:

[  
   {  
      "Key":"Attributed Touch Time",
      "Value":"2016-09-06 20:11:50"
   },
   {  
      "Key":"Install Time",
      "Value":"2016-09-06 20:14:12"
   },
   {  
      "Key":"Event Name",
      "Value":"install"
   }
]

Then I fixed my converter like so:

public abstract class JsonCreationConverter<T> : JsonConverter
{
    /// <summary>
    /// Create an instance of objectType, based properties in the JSON object
    /// </summary>
    /// <param name="objectType">type of object expected</param>
    /// <param name="jObject">
    /// contents of JSON object that will be deserialized
    /// </param>
    /// <returns></returns>
    protected abstract T Create(Type objectType, JObject jObject);

    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(List<KeyValuePair<string, string>>);
    }

    public override object ReadJson(JsonReader reader,
                                    Type objectType,
                                     object existingValue,
                                     JsonSerializer serializer)
    {
        // Load JObject from stream
        JObject jObject = JObject.Load(reader);

        // Create target object based on JObject
        T target = Create(objectType, jObject);

        // Populate the object properties
        serializer.Populate(jObject.CreateReader(), target);

        return target;
    }

    public override void WriteJson(JsonWriter writer,
                                   object value,
                                   JsonSerializer serializer)
    {
        List<KeyValuePair<string, string>> list = value as List<KeyValuePair<string, string>>;
        writer.WriteStartArray();
        foreach (var item in list)
        {
            writer.WriteStartObject();
            writer.WritePropertyName(item.Key);
            writer.WriteValue(item.Value);
            writer.WriteEndObject();
        }
        writer.WriteEndArray();
    }
}

But my Json object now looks like this:

[  
   {  
      "Attributed Touch Time":"2016-09-06 20:11:50"
   },
   {  
      "Install Time":"2016-09-06 20:14:12"
   },
   {  
      "Event Name":"install"
   },
(etc...) //Not part of JSON, just cutting it short
]

Which is great but still won't map to my entities

回答1:

It looks like you're creating a new JSON object for each KVP rather than grouping the KVP's into a single object. Move the writer.WriteStartObject(); and writer.EndObject(); to outside of the loop and you should end up with a nicely formed JSON Object.

   writer.WriteStartObject();

   foreach (var item in list)
    {

        writer.WritePropertyName(item.Key);
        writer.WriteValue(item.Value);

    }

    writer.WriteEndObject();
    writer.WriteEndArray();

You need to take those Start/End Objects to outside the For loop.

So you should get this instead...

[  
   {  
      "Attributed Touch Time":"2016-09-06 20:11:50"
      "Install Time":"2016-09-06 20:14:12"
      "Event Name":"install"
   },
]

来源：https://stackoverflow.com/questions/39583463/converting-json-object-to-data-entities-models-mymodel