API responding with Malformed JSON string

Question

I am trying to post data to an API but I am getting an error saying, "Malformed JSON string". I constructed my object based on the payload which I was given, which has been tested from python and is working fine.

What is it that am doing wrong based on my code below?

Original JSON payload which I have been given and I need to build from it .

{'i_customer': 1, 'custom_fields_values': [{'i_custom_field': 1, 'db_value': '2'}]}

My code attempt:

CustomField custom = new CustomField()
{
    CustomerId = customerId,
    CustomFieldsValues = new CustomFieldsValues()
    {
        CustomFieldId = _portaClient._CustomFieldId,
        DbValue = customFieldId
    }
};

var json = JsonConvert.SerializeObject(custom);
string url = string.Format(endpoint);
var client = new RestClient(url)
{
    Timeout = -1
};

var request = new RestRequest(Method.POST);
request.AddHeader("Content-Type", "application/x-www-form-urlencoded");
request.AddParameter("params", "{\"information\":" + json +  "\"}");
--              
var response = client.Execute(request);

The above code produces this payload:

{"i_customer":1,"custom_fields_values":{"i_custom_field":1,"db_value":"2"}}

API error response:

Error : "
{"faultcode":"malformed_json_string","faultstring":"Malformed JSON string"}"

This is my model

public class CustomField
{
    [JsonProperty(PropertyName = "i_customer")]
    public int? CustomerId { get; set; }

    [JsonProperty(PropertyName = "custom_fields_values")]
    public CustomFieldsValues CustomFieldsValues { get; set; }
}

public class UpdateCustomerCustomFieldsValuesResponse
{
    [JsonProperty(PropertyName = "i_customer")]
    public int? CustomerId { get; set; }
}

public class CustomFieldsValues
{
    [JsonProperty(PropertyName = "i_custom_field")]
    public int CustomFieldId { get; set; }

    [JsonProperty(PropertyName = "db_value")]
    public string DbValue { get; set; }
}

How can I fix this?

Answer 1

FWIW, I believe the error is not accurate. "Malformed" has a very specific meaning that does not apply here, in that your result is well-formed and valid JSON data. This valid JSON result isn't structured in a way their system would like, which is still an error... just not the same kind of error as sending "malformed" JSON.

To fix this things, this CustomField class:

public class CustomField
{
    [JsonProperty(PropertyName = "i_customer")]
    public int? CustomerId { get; set; }

    [JsonProperty(PropertyName = "custom_fields_values")]
    public CustomFieldsValues CustomFieldsValues { get; set; }
}

needs the CustomFieldsValues property to show as an array or list:

public class CustomField
{
    [JsonProperty(PropertyName = "i_customer")]
    public int? CustomerId { get; set; }

    [JsonProperty(PropertyName = "custom_fields_values")]
    public List<CustomFieldsValues> CustomFieldsValues { get; set; }
}

And then, of course, you must also update any code which populates this object accordingly:

CustomField custom = new CustomField() { 
    CustomerId = customerId, 
    CustomFieldsValues = new List<CustomFieldsValues> { 
        new CustomFieldsValues() {
           CustomFieldId = _portaClient._CustomFieldId, 
           DbValue = customFieldId 
        } 
    }
};

Finally, if they really do want single-quotes for field names, they've got a lot of nerve telling you your JSON is malformed, when in fact it is their own system using malformed and non-standard JSON.