C# JSON error => Cannot deserialize JSON object into type 'System.Collections.Generic.IEnumerable`1

Question

I am trying to access a .json endpoint with this line of code inside Main():

var RM= ParseArrayFromWeb<RM>("http://myendpoint.json").ToArray();              

Here is the ParseArrayFromWeb function that is defined above/outside of MAIN()

public static IEnumerable<T> ParseArrayFromWeb<T>(string url)
{
    var webRequest = WebRequest.Create(url);
    using (var response = webRequest.GetResponse())
    {
        if (response != null)
        {
            var stream = response.GetResponseStream();
            if (stream != null)
            {
                using (var reader = new StreamReader(stream))
                {
                    return JsonConvert.DeserializeObject<IEnumerable<T>>(reader.ReadToEnd());
                }
            }
        }
        throw new WebException("Options request returned null response");
    }
}

Here is the RM class that is defined above/outside of Main() that should hold the json fields returned:

public class RM
{

    public string calculation_method { get; set; } 
    public double? related_master_id { get; set; }
    public string related_master_name { get; set; }
    public string parameter_file_date { get; set; } 
    public string exchange_complex { get; set; }
    public string combined_commodity_code { get; set; }
    public string currency { get; set; }
    public double? maintenance_margin { get; set; }
    public double? scanning_risk { get; set; }
    public double? spread_charge { get; set; }
    public double? spot_charge { get; set; }
    public double? inter_commodity_credit { get; set; }
    public double? short_option_minimum { get; set; }
    public double? scenario_number { get; set; }
    public double? initial_margin { get; set; }
    public string exchange_code { get; set; } 
    public string product_description { get; set; }
    public string error_description { get; set; }
}

The error I am getting is:

Cannot deserialize JSON object into type 'System.Collections.Generic.IEnumerable`1[JSON.Program+RM]'.

HERE is one row of the JSON:

{"error_description":"error 454", "combined_commodity_code":"xx", "exchange_complex":"x", "exchange_code":"x", "initial_margin":null, "maintenance_margin":null, "scanning_risk":null, "spread_charge":null, "spot_charge":null, "currency":null," inter_commodity_credit":0},

Notice not all fields are present. That is ok. I have to handle that.

Any ideas?

Thank you.

Answer 1

The problem is with this instruction:

return JsonConvert.DeserializeObject<IEnumerable<T>>(reader.ReadToEnd());

You cannot deserialize to interfaces, since they cannot be instantiated, and the deserialization process, by nature, instantiate objects to store the data in the JSON. You need to use a concrete class for the deserialization, like this:

return JsonConvert.DeserializeObject<List<T>>(reader.ReadToEnd());

Hope this helps.