C# Json Deserialization with multiple class constructors

Question

Depending on the licence I query, I get two different JSON responses. On Success I get the "success" string and on error I get the "code" string. Now, I have built a two constructors class to catch both cases.

When I deserialize the json string with:

License license = JsonConvert.DeserializeObject<License>(json_str);

I get the error: "Unable to find a constructor to use for type..."

Here is the code, any suggestions:

 //JSON String on Success -> {"success":true,"data":{"id":54,"orderId":109,"productId":79,"userId":1,"licenseKey":"1y10a3P-YL-A1-EQ-F9-GI-DM-W3","expiresAt":"2022-09-04 09:02:40","validFor":365,"source":1,"status":2,"timesActivated":null,"timesActivatedMax":1,"createdAt":"2021-09-04 09:02:40","createdBy":0,"updatedAt":"2021-09-04 09:02:40","updatedBy":0}}
 //JSON String on error -> {"code":"lmfwc_rest_license_expired","message":"The license Key expired on 2021-10-06 00:00:00 (UTC).","data":{"status":405}}

    public partial class License
    {
        [JsonProperty("success")]
        public bool Success { get; set; }

        [JsonProperty("data")]
        public Success_Data Success_Data { get; set; }

        [JsonProperty("code")]
        public String Code { get; set; }

        [JsonProperty("message")]
        public String Message { get; set; }

        [JsonProperty(PropertyName = "error_data")]
        public Error_Data Error_Data { get; set; }

        public License(bool success, Success_Data data)
        {
            Success = success;
            Success_Data = data;
        }

        public License(String code, String message, Error_Data error_data)
        {
            Code = code;
            Message = message;
            Error_Data = error_data;
        }
    }

    public partial class Error_Data
    {
        [JsonProperty("status")]
        public long Status { get; set; }
    }        

    public partial class Success_Data
    {
        [JsonProperty("id")]
        public long Id { get; set; }

        [JsonProperty("orderId")]
        public long OrderId { get; set; }

        [JsonProperty("productId")]
        public long ProductId { get; set; }

        [JsonProperty("userId")]
        public long UserId { get; set; }

        [JsonProperty("licenseKey")]
        public string LicenseKey { get; set; }

        [JsonProperty("expiresAt")]
        public DateTimeOffset ExpiresAt { get; set; }

        [JsonProperty("validFor")]
        public object ValidFor { get; set; }

... }

I think JSON serialization requires a default constructor (i.e., one without any parameters). Your License type doesn't have one — Flydog57
– Flydog57, Commented Nov 1, 2021 at 14:18
@Flydog57 is correct, you need a default, parameterless constructor. For example: public License(){} If you still want to use a constructor other than the default, add [JsonConstructor] attribute to that constructor. Here's a little information about that. — Trevor
– Trevor, Commented Nov 1, 2021 at 14:34

Serge · Accepted Answer · 2021-11-01 15:47:05Z

1

you need a constructor with [JsonConstructor] attribute. This code was tested and works properly

[JsonConstructor]
public License(String code, String message, JToken data, bool? success = null)
{
    if (success != null)
    {
        Success = (bool)success;
        Success_Data = JsonConvert.DeserializeObject<Success_Data>(data.ToString());
    }
    else
    {
        Code = code;
        Message = message;
        Error_Data = JsonConvert.DeserializeObject<Error_Data>(data.ToString());
    }
}

and remove [JsonProperty(PropertyName = "error_data")] since there is no this json property. Leave just

 public Error_Data Error_Data { get; set; }

edited Nov 1, 2021 at 15:47

answered Nov 1, 2021 at 15:11

Serge

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2 Comments

paralax Over a year ago

Thanks Serge, didn't try yet, but make sense, I will try and give feedback!

paralax Over a year ago

Thanks, that did the magic!!!

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