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System.Text.Json JsonSerializer: Serialization and deserialization of 'System.Type' instances are not supported

I got an error related with security when I tried to deserialize by using `System.Text.Json JsonSerializer`.
What do I want to achieve?
I want to give the user controle to transalte some records in my database, so use can follow this scenario:
1- User can choose model of my class library.
2- After selecting a class, user will select a property(filed) from this class.
3- User will get list of values of the selected property up.
4- Last step is not here right now, user can edit a certian value.
This my piece of code:
MyPage.razor.cs:
[Inject]
private IGenericHttpClient<Type> HttpClient { get; set; }
private Type SelectedType { get; set; }
// First select a class [Class library] from HTML Select
private void OnTypeChnage(ChangeEventArgs args)
{
string FullName = "My.Models." + args.Value.ToString();
// Create type of selected class
SelectedType = Assemble.GetType(FullName, false);
}
//Call api to get all fields of this class
private async Task OnPropertChange(ChangeEventArgs args)
{
var list = await
HttpClient.GetJsonAsync($"/api/{SelectedType.Name}/all");
}
GenericHttpClient.cs
public async ValueTask<List<T>> GetJsonAsync(string url)
{
using HttpResponseMessage response = await _client.GetAsync(url);
ValidateResponse(response);
var conetnt = await response.Content.ReadAsStringAsync();
//I got the error down
return JsonSerializer.Deserialize<List<T>>(conetnt, new JsonSerializerOptions() { PropertyNameCaseInsensitive=true});
}

System.Text.Json does not support Type class due to security reasons. You send the full assembly name as a string and again try to construct the Type at the client end.

public async ValueTask<List<T>> GetJsonAsync(string url) this wont even compile, due to not specify generic information on method signature.
And also, your problem would come from the content of http response, otherwise, the Deserialize step should work fine.
I copied your code and make a small block that prove it.
// Define somewhere
public class GenericHttpClient
{
public List<T> GetJsonAsync<T>()
{
var content = "[{\"TestProp\": \"This is some test\"}]";
return JsonSerializer.Deserialize<List<T>>(content, new JsonSerializerOptions() { PropertyNameCaseInsensitive=true});
}
}
public class Test
{
public string TestProp { get; set; }
}
// Test it
var test = new GenericHttpClient();
var result = test.GetJsonAsync<Test>();

Like what #Mayur Ekbote mentioned up, "System.Text.Json does not support Type class due to security reasons." I will add a solution but I don't think this solution is very efficient.
Change Type to Dynamic:
[Inject]
private IGenericHttpClient<dynamic> HttpClient { get; set; }
Use JsonElement to get the value as a string:
private async Task OnPropertChange(ChangeEventArgs args)
{
var langCode = CultureInfo.CurrentCulture.Name;
PropertyValueList.Clear();
var list = await HttpClient.GetJsonAsync($"/api/{SelectedType.Name}/all");
List<object> listValue = new List<object>();
SelectedProperty = args.Value.ToString();
string fieldName = char.ToLower(SelectedProperty[0]) + SelectedProperty.Substring(1);
foreach (var item in list)
{
//Convert object to JsonElement
var val = ((JsonElement)item).GetProperty(fieldName).GetString();
PropertyValueList.Add(val);
}
}
Why is it not efficient?
Because I got a list of value String instead of list of selected class.

Converting a JSON into own type results in null objects

from my rest call, I am receiving this JSON:
{
"livemode": true,
"error": {
"type": "unauthorized",
"message": "You did not provide a valid API key."
}
}
I need to fetch type and message into my type:
public class TestObject
{
string type { get; set; }
string message { get; set; }
}
But this returns null objects:
HttpClient client = new HttpClient();
Uri uri = new Uri("https://api.onlinebetaalplatform.nl/v1");
HttpResponseMessage response = await client.GetAsync(uri);
string content = await response.Content.ReadAsStringAsync();
JObject json = JObject.Parse(content);
TestObject album = json.ToObject<TestObject>();
1.) I understand that the type and message attributes are "nested". How do I access them?
2.) Even if I call my type livemode and error, the objects still return null.
Can you help me out a little?
Thank you :)

There seems to be one set of curly brackets to many. I am pretty sure that the api you are querying is not returning the first and the last curly bracket. Continue on after that has been taken care of.
In order to fetch the data, add these class definitions
public class Error
{
public string type { get; set; }
public string message { get; set; }
}
public class Root
{
public bool livemode { get; set; }
public Error error { get; set; }
}
and change
TestObject album = json.ToObject<TestObject>();
To
Root album = json.ToObject<Root>();
As some of the comments to your question mentioned, you are currently trying to convert the JSON string to the nested Error object instead of the root object, where the Error object is located.
In the future, there are tools that can generate C# classes from JSON. I used https://json2csharp.com/ this time around to do so.
EDIT:
I just found out that Visual Studio actually has an in-built JSON to Class feature!

How to bind JSON response from httpClient.PostAsJsonAsync

I can httpClient.PostAsJsonAsync(path, content) fine.
However, this post returns some JSON with details of the response, eg:
{"StatusCode":200,"AccessCode":"92BEEB285ZB47DA","InternalMessage":null}
I need to access the AccessCode.
How can I do this cleanly and efficiently? Can I create an object like this:
public class GIResponse
{
public string StatusCode { get; set; }
public string AccessCode { get; set; }
public string InternalMessage { get; set; }
}
And map it to the result?
Or how would I just traverse the JSON and pull out the AccessCode?
I have searched quite extensively but surprisingly I can't find anything on Google - perhaps as this is the result from a Post, not a Get.
How can I do this?

Provided that you get the responseText using httpResponse.Content.ReadAsStringAsync, you can use Json.NET's JObject and define it as dynamic:
dynamic j = JObject.Parse(#"{""StatusCode"":200,""AccessCode"":""92BEEB285ZB47DA"",""InternalMessage"":null}");
Console.WriteLine(j.AccessCode);
Also you can use JsonConvert:
var result = JsonConvert.Deserialize<MyModel>(resposeText);
Obviously, if you already have a model, you do not read it as a string and you can simply read it as your model:
var result = httpResponse.Content.ReadAsAsync<MyModel>();

How to correctly deserialise JSONArrays using RestSharp

How do I correctly deserialise the results of this call (you can click to see output):
https://bitpay.com/api/rates
I'm using a POCO object like this:
public class BitpayPrice
{
public string code { get; set; }
public string name { get; set; }
public double rate { get; set; }
}
And I'm calling the API like so:
var client = new RestClient();
client.BaseUrl = "https://bitpay.com";
var request = new RestRequest("/api/rates", Method.GET);
var response = client.Execute<BitpayPrice[]>(request);
Now, I know that the call to execute is wrong, but how do I un-wrongify it? I'd like to get back an array of BitcoinPrice objects.

RestSharp doesn't support deserializing into array, the best you can get is a List<>:
var response = client.Execute<List<BitpayPrice>>(request);
The reason is that types that you can deserialize to are required to have public parameterless constructor (for performance reasons mostly).

Dealing with fanart.tv webservice response JSON and C#

I am trying to use the fanart.tv webservice API but have a couple of issues.
I am using Json.Net (Newtonsoft.Json) and with other web-services I have de-serialized the JSON reponses into C# objects directly.
The issue here is that the element names are changing. Eg. if I search for artist thumbs for Metallica you get
{"Metallica":{"mbid_id":"65f4f0c5-ef9e-490c-aee3-909e7ae6b2ab","artistthumb": [{"id":"36181","url":"http://assets.fanart.tv/fanart/music/65f4f0c5-ef9e-490c-aee3-909e7ae6b2ab/artistthumb/metallica-4fd83b0129f83.jpg","likes":"1"},...]}}
So the root element is called Metallica. Obviously search for another artist and you get a different element name. After attempting to deserialize this to an object I gave up and as in reality all I needed was a list of strings (the urls) I tried to process the JSON
var obj = _downloader.Download<JObject>(url);
if (obj != null)
{
if (obj.HasValues)
{
var fanartArtist = (JProperty)obj.First;
if (fanartArtist.HasValues)
{
var thumbs = fanartArtist.Value[SearchSubTypeToString(subType)];
if (thumbs.HasValues)
{
thumbUrls.AddRange(thumbs.Select(thumb => thumb["url"].ToString()));
}
}
}
}
which works fine when there is a response but if there are no thumbs the web-service returns null and this code fails with
Unable to cast object of type 'Newtonsoft.Json.Linq.JValue' to type 'Newtonsoft.Json.Linq.JObject'.
To complicate matters slightly I am sort of limited by the application and ideally I need to use
JsonConvert.DeserializeObject<TE>(json);
So the question is what what is the best approach to solve both of these issues?

Try this:
First, define objects to hold the data deserialized from the JSON:
class Artist
{
public Guid mb_id { get; set; }
public List<Thumb> artistthumb { get; set; }
}
class Thumb
{
public int id { get; set; }
public string url { get; set; }
public int likes { get; set; }
}
You can then deserialize it like this (where json is a string containing the JSON data from the web service):
Dictionary<string, Artist> artists =
JsonConvert.DeserializeObject<Dictionary<string, Artist>>(json);
Once deserialized, you can access the data like this:
foreach (KeyValuePair<string, Artist> kvp in artists)
{
Console.WriteLine("Urls for " + kvp.Key + ":");
foreach (Thumb thumb in kvp.Value.artistthumb)
{
Console.WriteLine(thumb.url);
}
}
Assuming the data you showed in your question, the output would look like this:
Urls for Metallica:
http://assets.fanart.tv/fanart/music/65f4f0c5-ef9e-490c-aee3-909e7ae6b2ab909e7ae6b2ab/artistthumb/metallica-4fd83b0129f83.jpg
.