C#•15mo ago

❔ Deserializing JSON

I'm working on a project where I need to deserialize a JSON api response, and do things with the data. This is a little demo thing:

class Response {
    [JsonProperty("success")]
    [DefaultValue(false)]
    public bool Success { get; private set; }

    [JsonProperty("days")]
    public Days Days { get; private set; }
}

class Days {
    [JsonProperty("first_day")]
    [DefaultValue("monday")]
    public string FirstDay { get; private set; }
}

class Response {
    [JsonProperty("success")]
    [DefaultValue(false)]
    public bool Success { get; private set; }

    [JsonProperty("days")]
    public Days Days { get; private set; }
}

class Days {
    [JsonProperty("first_day")]
    [DefaultValue("monday")]
    public string FirstDay { get; private set; }
}

My issue is, I need to be able to use Response.Days.FirstDay, when my JSON response looks like this: {'success': true, 'first_night': 'friday'} Essentially, I want the DefaultValue to be present, even if the JSON doesn't contain the 'first_day' key. I'm really not sure how to do this, because I'd need to do this with dozens of attributes in about 6 subclasses, so doing it all manually would take ages and doesn't seem good for maintainability. Any help on how I can achieve this result? To get everything to 'exist' even if it doesn't exist in the JSON, just by using the default value?

6 Replies

Angius•15mo ago

Well, you can have the optional property be nullable Then, whenever you access it, simply provide a fallback object.MaybeNull ?? 0

Pobiega•15mo ago

What about using [JsonConstructor] to set the defaults?

Angius•15mo ago

Or that, yeah

illyOP•15mo ago

How can I use that?

Pobiega•15mo ago

public static class Program
{
    public static void Run()
    {
        var options = new JsonSerializerOptions(JsonSerializerDefaults.Web)
        {
            WriteIndented = true
        };

        var json =
            """
            {
                "success": true,
                "days": {
                    "first_night": "friday"
                }
            }
            """;

        var deser = JsonSerializer.Deserialize<Root>(json, options);
        var jsonAgain = JsonSerializer.Serialize(deser, options);
        Console.WriteLine(jsonAgain);
    }
}

public class Root
{
    public bool Success { get; set; } = false;
    public Days Days { get; set; }
}

public class Days
{
    [JsonPropertyName("first_day")] public string FirstDay { get; set; } = "monday";
}

public static class Program
{
    public static void Run()
    {
        var options = new JsonSerializerOptions(JsonSerializerDefaults.Web)
        {
            WriteIndented = true
        };

        var json =
            """
            {
                "success": true,
                "days": {
                    "first_night": "friday"
                }
            }
            """;

        var deser = JsonSerializer.Deserialize<Root>(json, options);
        var jsonAgain = JsonSerializer.Serialize(deser, options);
        Console.WriteLine(jsonAgain);
    }
}

public class Root
{
    public bool Success { get; set; } = false;
    public Days Days { get; set; }
}

public class Days
{
    [JsonPropertyName("first_day")] public string FirstDay { get; set; } = "monday";
}

I decided to use properties with default values instead of a constructor this outputs

{
  "success": true,
  "days": {
    "first_day": "monday"
  }
}

{
  "success": true,
  "days": {
    "first_day": "monday"
  }
}

Accord•15mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Deserializing JSON