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c#deserializationdotnet-httpclientnullreferenceexception
Win Sunday
Win Sunday

Reputation: 3

how to handle" System.InvalidCastException: when Deserializing the result of an API call

I am not sure I framed the title properly, but I hope i get some assistance regardless. I am trying to consume an api but i keep getting "JsonSerializationException: Error converting value {null} to type 'System.Double". This happens when I try to deserialize in the line labeled as Error Line in the code just at the bottom

var response = JsonConvert.DeserializeObject<GetSalaryHistoryResponse>();

During the API call, I noticed about two fields with null values, which could be what is triggering the error

using (var client = new HttpClient())
{
    client.BaseAddress = new Uri(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx);

    client.DefaultRequestHeaders.Add("API_KEY", "xxxxxxxxxxxxxxxxxxx");
    client.DefaultRequestHeaders.Add("REQUEST_ID", "xxxxxxxx");
    client.DefaultRequestHeaders.Add("MERCHANT_ID", "xxxxxxxx");
    client.DefaultRequestHeaders.TryAddWithoutValidation("AUTHORIZATION", "ConsumerKey=Q1dHREVNTzEyMzR8Q1dHREVNTw==,ConsumerToken=c5e8db0cbca54593e54f6702778d1ea129463d5555166cd1d0c46416495df82483a08c30fdd1e9fa39ceeea9bc6d8da9ba892ff3c3f326d537bc06bf8ef3ece7");

    string vv = request.ToJson();
    var content = new StringContent(request.ToJson(), System.Text.Encoding.UTF8, "application/json");
    var responseTask = client.PostAsync("provideCustomerDetails", content);
    responseTask.Wait();
    var result = responseTask.Result;
    if (result.IsSuccessStatusCode)
    {
        var readTask = result.Content.ReadAsStringAsync();
        readTask.Wait();
        var a = readTask.Result.ToString();
***Error Line:>* **     var response = JsonConvert.DeserializeObject<GetSalaryHistoryResponse>(readTask.Result);
         
        return response ;
    }
}

I saw a hint to use the code snippet below, I also replaced attributesObject with the class property and still get the error. I can't seem to figure out how to do this. i just want to be able to send the value of the Deserialization as a return value and use it elsewhere, can anyone help ?

var json = JsonConvert.SerializeObject(
    attributesObject,      
    Formatting.None,
    new JsonSerializerSettings
    {
        NullValueHandling = NullValueHandling.Ignore
    });

Upvotes: 0

Views: 69

Answers (1)

ssedlacek
ssedlacek

Reputation: 196

do not use .Result, or .Wait method if you don't want to use async/await in the method. Use .GetAwaiter().GetResult() in this case. I could imagine your method similar to this:

var response = client.PostAsync("provideCustomerDetails", content).GetAwaiter().GetResult();

if (response.IsSuccessStatusCode) 
{
   var content = response.Content.ReadAsStringAsync().GetAwaiter().GetResult();
   var deserialized = JsonConvert.DeserializeObject<DesiredTypeHere>(content, new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore });
   return deserialized;
}

Upvotes: -1

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