How Can I deserialize a json into a structure?

Erick Published at Dev

Erick

I have a class mapping like this:

public class Settings
{
    [JsonProperty("id")]
    public string Id { get; set; }

    [JsonProperty("type")]
    public string Type { get; set; }

    [JsonProperty("content")]
    public ContentStructure Content { get; set; }
}


public struct ContentStructure
{
    public Content ContentClass;
    public string ContentString;

    public static implicit operator ContentStructure(Content content) => new ContentStructure { ContentClass = content };
    public static implicit operator ContentStructure(string @string) => new ContentStructure { ContentString = @string };
}


public class Content
{
    [JsonProperty("id")]
    public string Id { get; set; }

    [JsonProperty("duration")]
    public long Duration { get; set; }
}

When I attempt to deserialize the following JSON string:

{
    "id": "any_id",
    "type": "any_type",
    "content": {
        "id": "any_id",
        "duration": 1000
    }
}

I always get the deserialized settings object with the property settings.Content.ContentClass null, but whenever my JSON string has the property "content" as string (instead of an object) the structure field ContentString comes correctly. What I am doing wrong? How can I can convert the JSON string above correctly?

Peter Csala

Yet another solution could be to make use of the JsonSchema

First let's redefine your data model:

public abstract class Settings
{
    [JsonProperty("id")]
    public string Id { get; set; }

    [JsonProperty("type")]
    public string Type { get; set; }
}

public class SettingsV1 : Settings
{
    [JsonProperty("content")]
    public string Content { get; set; }
}

public class SettingsV2 : Settings
{
    [JsonProperty("content")]
    public Content Content { get; set; }
}

public class Content
{
    [JsonProperty("id")]
    public string Id { get; set; }

    [JsonProperty("duration")]
    public long Duration { get; set; }
}

Instead of having a middle man (ContentStructure) rather than you can have two separate Settings versions
The common fields are defined inside the abstract base class

Now, you can use these two versioned classes to define json schemas:

private static JSchema schemaV1;
private static JSchema schemaV2;

//...
var generator = new JSchemaGenerator();
schemaV1 = generator.Generate(typeof(SettingsV1));
schemaV2 = generator.Generate(typeof(SettingsV2));

Finally all you need to do is to do a preliminary check before calling the DeserializeObject with the proper type:

Settings settings = null;
var semiParsed = JObject.Parse(json);
if (semiParsed.IsValid(schemaV1))
{
    settings = JsonConvert.DeserializeObject<SettingsV1>(json);
}
else if (semiParsed.IsValid(schemaV2))
{
    settings = JsonConvert.DeserializeObject<SettingsV2>(json);
}
else
{
    throw new NotSupportedException("The provided json format is not supported");
}

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