Blazor Server - deserializing an array of objects with System.Text.Json - The JSON value could not be converted to .....

Question

User379720387 posted

The JSON value could not be converted to BtServer.Pages.RecordDetail+MyRecordDetails. Path: $ | LineNumber: 0 | BytePositionInLine: 1.

   at System.Text.Json.ThrowHelper.ThrowJsonException_DeserializeUnableToConvertValue(Type propertyType)
   at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
   at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
   at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   at System.Text.Json.JsonSerializer.ReadCore[TValue](Utf8JsonReader& reader, Type returnType, JsonSerializerOptions options)
   at System.Text.Json.JsonSerializer.Deserialize[TValue](String json, Type returnType, JsonSerializerOptions options)
   at System.Text.Json.JsonSerializer.Deserialize[TValue](String json, JsonSerializerOptions options)
   at BtServer.Pages.RecordDetail.<OnInitializedAsync>d__12.MoveNext() in C:\Users\Robert\source\Repos\BtApiCore5\BtServer\Pages\RecordDetail.razor:line 92

public class MyRecordDetails
    {
        public IEnumerable<RecordDetail> details { get; set; }   

        //tried this one too! same error message: public List<RecordDetail> details { get; set; } 
    }
        

    protected override async Task OnInitializedAsync()
    {
        try
        {
            var httpClient = _clientFactory.CreateClient("ServerAPI");
            httpClient.DefaultRequestHeaders.Add("Accept", "application/json");

            var json = JsonSerializer.Serialize(recordDetails);
            var content = new StringContent(json);
            
            content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/json");

            var options = new JsonSerializerOptions()
            {
                PropertyNamingPolicy = JsonNamingPolicy.CamelCase
            };

            HttpResponseMessage response = await httpClient.GetAsync($"{baseUrl}/api/Record/DetailByClient/22/49/3");
            
            
            string dtls = await response.Content.ReadAsStringAsync();
                  
            if (dtls is not null)
            {
                MyRecordDetails details = JsonSerializer.Deserialize<MyRecordDetails>(dtls, options);
            }
            else
            {
                //do something    
            }
            
        }
        catch (Exception ex) { Console.WriteLine(ex.Message); }                
    }

dtls holds: 

[
{"TransactionId":1015,"CName":"Don","TDate":"May  9 2020  4:54PM","BDate":"May  9 2020  4:54PM","Initials":"JMC","IsBilled":false,"IsPaid":false,"SvcLevel":"R1"},
{"TransactionId":988,"CName":"Don","TDate":"Jan 23 2020  3:13PM","BDate":"Mar 10 2020 11:17AM","Initials":"JMC","IsBilled":false,"IsPaid":false,"SvcLevel":"R1"},
{"TransactionId":974,"CName":"Don","TDate":"Jan 22 2020  2:36PM","BDate":"Jan 22 2020  2:36PM","Initials":"JMC","IsBilled":false,"IsPaid":false,"SvcLevel":"R1"}
]

Online deserializers have no problem deserializing dtls

public class RecordDetail
    {
        public int TransactionId { get; set; }
        public string CName { get; set; }
        public string TDate { get; set; }
        public string BDate { get; set; }
        public string Initials { get; set; }
        public bool IsBilled { get; set; }
        public bool IsPaid { get; set; }
        public string SvcLevel { get; set; }
        
        //public List<ServiceItem> ServiceItems { get; set; }
        //public List<ShoeItem> ShoeItems { get; set; }
        //public List<FileItem> FileItems { get; set; }
        //public List<ImageItem> ImageItems { get; set; }
        //public List<NoteItem> NoteItems { get; set; }
        //public List<VoiceItem> VoiceItems { get; set; }
    }

What am I doing wrong?

Answer 1

User-943250815 posted

Back to your original intention, collect to a List.
Give a try to, your as is looks fine for a single record, but you are readind an array

List<MyRecordDetails> details = JsonSerializer.Deserialize<List<MyRecordDetails>>(dtls, options);

Answer 2

User379720387 posted

List<MyRecordDetails> details = JsonSerializer.Deserialize<List<MyRecordDetails>>(dtls, options);

Returns details which has 3 members, each of them null

Answer 3

User-474980206 posted

You don’t show the class definition of MyRecordDetails

Answer 4

User379720387 posted

@bruce (sqlwork)

This is all I have for MyRecordDetails, don't know if I am missing something:

public class MyRecordDetails
    {
        public IEnumerable<RecordDetail> details { get; set; }           
    }

Answer 5

User-943250815 posted

Oops, I mistyped my sample above, here the correct one, using it you should get a list with 3 elements and values filled correctly.
But don´t use "options" other than values will not be filled

List<RecordDetail> details = JsonSerializer.Deserialize<List<RecordDetail>>(dtls);

Answer 6

User753101303 posted

Hi,

Or

MyRecordDetails details = new MyRecordDetails();details.details=JsonSerializer.Deserialize<List<RecordDetail>>(dtls);

Your json is a list of RecordDetail and you are confusing this with MyRecordDetails which is a single object having a property which is a list of RecordDetail and which is perhaps not needed.

.

Answer 7

User379720387 posted

@jzero

Without "options" it hangs and there are no exceptions shown in VS or in browser console

@PatriceSc

That maybe so, I don't know.  Nothing works at this point, just throwing code on the wall and hope something sticks. So far I have been able to produce 3 elements (which matches what it is supposed to find)  but each element is null.

Answer 8

User-943250815 posted

Here is what I did:
1) Place your JSON sample above in a text file
2) Make a file with your class and a routine to read file and deserialize JSON into a List

public class RecordDetail
  {
    public int TransactionId { get; set; }
    public string CName { get; set; }
    public string TDate { get; set; }
    public string BDate { get; set; }
    public string Initials { get; set; }
    public bool IsBilled { get; set; }
    public bool IsPaid { get; set; }
    public string SvcLevel { get; set; }
  }

void ReadJSonFromFile()
{
string MyFile = @"C:\sample.json";
string MyJsonStr = System.IO.File.ReadAllText(MyFile);
List<RecordDetail> DetailsNoOptions = System.Text.Json.JsonSerializer.Deserialize<List<RecordDetail>>(MyJsonStr);
var options = new System.Text.Json.JsonSerializerOptions() {PropertyNamingPolicy = System.Text.Json.JsonNamingPolicy.CamelCase};
List<RecordDetail> DetailsWithOptions = System.Text.Json.JsonSerializer.Deserialize<List<RecordDetail>>(MyJsonStr, options);
}

This results:
DetailsNoOptions = 3 itens, data filled with values from Json;
DetailsWithOptions = 3 itens, data filled with null

Answer 9

User379720387 posted

Ok, figured it out.

I have a "view model" called RecordDetail.cs, you have seen it in this thread, it lives in the Web API project.

I also have a RecordDetail.razor page, it lives in the Blazor Server project

When you declare this:

private List<RecordDetail> recorddetails;

It is making  List<RecordDetails.blazor> apparently.  That fails silently, there are no warnings about ambiguity.

Too many leaves up in the air, and focused on the wrong leaf (deserialization).

Thanks all for contributing taking some of these leaves out of the air.