getting 'System.Text.Json.JsonElement' does not contain 'result' Parsing with JsonSerializer.DeserializeAsync

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I have JSON in a response structured like this

{
   "statusCode": 200,
   "result": {
      "generalInfo": {
         "firstName": "",
         "lastName": ""
      },
      "isError": false      
   },
   "sentDate": "2022-02-06T10:04:06.6853775Z",
}

var response = await _httpClient.PostAsJsonAsync(address, model);
Stream responseBody = await response.Content.ReadAsStreamAsync();

The response from the endpoint is actually a bit more complex and I want to extract only specific fields so I used dynamic

dynamic data = await JsonSerializer.DeserializeAsync<dynamic>(responseBody)

var dataString = data.ToString();

// dataString is

{"result":{"generalInfo":{"firstName":"John","lastName":"Doe"},"isError":false}

If I try to access dynamic properties like this

var firstName = data.result.generalInfo.firstName;
var lastName = data.result.generalInfo.lastName;
var isErr = data.IsError;

I'm getting exception

'System.Text.Json.JsonElement' does not contain a definition for 'result'

system.text.json .net c#
1 Answers

The problem is not DeserializeAsync, but that System.Text.Json uses JsonElements, so the dynamic value is actually a JsonElement. You'll need to parse the data from the JsonElement.

However, if you're using .Net 6 you can use JsonNode:

// deserialize into JsonNode
JsonNode data = await JsonSerializer.DeserializeAsync<JsonNode>(responseBody);
// OR parse the json string
JsonNode data = JsonNode.Parse(dataString);

int statusCode = (int)data["statusCode"];
var firstName = (string)data["result"]["generalInfo"]["firstName"];
var lastName = (string)data["result"]["generalInfo"]["lastName"];
var isErr = (bool)data["result"]["isError"];

Demo in .Net6

Support for dynamic was added to .Net 6 preview v4-6 but was removed before final release in favour of the JsonNode approach above. See github What's new in .NET 6 Preview 7 for further details.

Otherwise, you could parse it manually:

bool isError = false;
string firstName = ""; 
string lastName = "";
if (data is JsonElement elt && elt.TryGetProperty("result", out elt))
{
    isError = elt.TryGetProperty("isError", out JsonElement boolElt) ? boolElt.GetBoolean() : false;
    if (elt.TryGetProperty("generalInfo", out var genInfo))
    {
        firstName = genInfo.TryGetProperty("firstName", out var firstElt) ? firstElt.GetString() : "";
        lastName = genInfo.TryGetProperty("lastName", out var lastElt) ? lastElt.GetString() : "";
    }
}

However, my preferred approach is always to deserialize into defined classes if you can as it makes life much easier:

public class GeneralInfo
{
    public string firstName { get; set; }
    public string lastName { get; set; }
}

public class Result
{
    public GeneralInfo generalInfo { get; set; }
    public bool isError { get; set; }
}

public class Root
{
    public Result result { get; set; }
}

var data = await JsonSerializer.DeserializeAsync<Root>(responseBody);
var firstName = data.result.generalInfo.firstName;
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