SerializationException: There was an error deserializing the object of type ...Encountered unexpected character '<'.

Question

SerializationException: There was an error deserializing the object of type ...Encountered unexpected character '<'.

lm1212 141

I have just started making an app (following someone) using a movie API from tmdb. There appears to be an issue with the HTTP request or the api's response, as I am getting the error listed below:

SerializationException: There was an error deserializing the object of type MoviePro.Models.TMDB.MovieSearch. Encountered unexpected character '<'.

I have read through some other similar threads expressing the same issue, but have not been able to resolve my problem yet.
I am not very familiar with deserialization and using associated http classes etc.. yet. (Would like to be).
When I debug and place a checkpoint on the error (line 105) I get the 2 properties "readTimeout" and "writeTImeout" of the response variable "responseStream" set to false. I am finding it hard to investigate further form here and see exactly where the problem is.
If someone is able to take a quick look and tell me where to problem is coming from I will be most grateful.
The GitHub Repository link is pasted below. Thank you.
https://github.com/Lm768184/MPro

AgaveJoe 30,126 Reputation points

2022-05-19T14:03:14.337+00:00

This error means the response is HTML not JSON. Use the Visual Studio debugger to physically read the response. It could be an error or simply a standard HTML page.

Anonymous

Agree with AgaveJoe, perhaps the response is HTML.

You can try to use HttpResponseMessage.Content.ReadAsStringAsync() method to get the response content as string, and then check it.

Here is a sample about consuming the Asp.net core API using httpclient, you can refer to it.

API method:

[Route("GetCustomers")]
[HttpGet]
public List<CustomerModel> GetCustomers(string name)
{
    return (from c in this.Context.Customers.Take(10)
            where c.ContactName.StartsWith(name) || string.IsNullOrEmpty(name)
            select c).ToList();
}

Consume the API method:

List<CustomerModel> customers = new List<CustomerModel>();
string apiUrl = "https://localhost:44318/api/CustomerAPI";

HttpClient client = new HttpClient();
HttpResponseMessage response = client.GetAsync(apiUrl + string.Format("/GetCustomers?name={0}", name)).Result;
if (response.IsSuccessStatusCode)
{
    customers = JsonConvert.DeserializeObject<List<CustomerModel>>(response.Content.ReadAsStringAsync().Result);
}

lm1212 141 Reputation points

2022-05-24T03:20:48.063+00:00
Thanks for your help. I have tried a few different things and have not been able to get it to work. The MemoryStream system.io.read and write timeouts happen anyway from what I have read, so I can rule them out as being the problem. I tried using the JsonConvert.SerializeObject() method as suggested by Zhilv above (code below), but now I am getting the error "SerializationException: Expecting element 'root' from namespace ''.. Encountered 'None' with name '', namespace ''. " I am quite stuck on this, and would appreciate any more advice. Thank you.

var response2 = client.GetAsync(requestUri).Result;

if (response2.IsSuccessStatusCode) { var t = response2.Content.ReadAsStringAsync().Result; var d = JsonConvert.SerializeObject(t); var dcjs = new DataContractJsonSerializer(typeof(MovieSearch)); MemoryStream stream = new(); dcjs.WriteObject(stream, d); movieSearch = (MovieSearch)dcjs.ReadObject(stream); } return movieSearch;
Anonymous

2022-05-24T06:52:40.61+00:00
var t = response2.Content.ReadAsStringAsync().Result;

Try to set a break point to check the t value. What it looks like, a Json string or Html page?

var d = JsonConvert.SerializeObject(t);

After getting the response result, the t value should be a json string, then, we can use the JsonConvert.DeserializeObject() method to convert the json string to object, instead of the JsonConvert.SerializeObject method (this method is used to convert the an Object to a Json string).
lm1212 141 Reputation points

2022-05-24T08:28:24.9+00:00
var t = response2.Content.ReadAsStringAsync().Result;

If I click the down arrow next to the variable t in running (I use a breakpoint to stop the code there) all 3 options - Text, XML and HTML visualiser produce values, the text has a lot of data (starts with <!DOCTYPE html>), the XML value just reads " Upcoming Movies — The Movie Database (TMDB) " and the HTML value produces content we'd expect to find on a web page - links headings etc.. Basically the HTML rendered.

The other 1 option in the dropdown menu - JSON visualiser, produces the same value as the HTML page, except that it has a warning icon above the value container, which reads "String is not JSON formatted".

I wrote:

var d = JsonConvert.SerializeObject(t);

All the line above does is add [JSON]: to line 0 positon 0 of the JSON visualizer (when inspecting after placing breakpoint, (d is the same as t except is has [JSON]: in front of <!DOCTYPE html> in the JSON visualizer). It does not help though as when I write:

var t = response2.Content.ReadAsStringAsync().Result; var e = JsonConvert.DeserializeObject<MovieSearch>(t);

I get the same error as before: "encountered unexpected "<".

So the issue appears to me that the DeserializeObject method is still getting HTML instead of JSON.

Is there code / method which takes the incoming HTML file and transfers it to JSON, so i can then deserialize it?
Anonymous

2022-05-25T09:23:49.19+00:00

Yes, when using the DeserializeObject method, it required a JSON string, instead of the html.

Since we don't know what's the HTML content looks like, so can't directly give a answer, but you can try to use Regex.Match or String method (such as find or Substring) to get the data from the HTML content and then generate the JSON string.

Besides, if you can modify the API method, you can change the return data from html format to a JSON format, this might be more easier.

1 answer

Your answer

AgaveJoe 30,126 Reputation points

2022-05-19T14:03:14.337+00:00

This error means the response is HTML not JSON. Use the Visual Studio debugger to physically read the response. It could be an error or simply a standard HTML page.
Anonymous

2022-05-20T07:03:28.113+00:00

Agree with AgaveJoe, perhaps the response is HTML.

You can try to use HttpResponseMessage.Content.ReadAsStringAsync() method to get the response content as string, and then check it.

Here is a sample about consuming the Asp.net core API using httpclient, you can refer to it.

API method:

[Route("GetCustomers")] [HttpGet] public List<CustomerModel> GetCustomers(string name) { return (from c in this.Context.Customers.Take(10) where c.ContactName.StartsWith(name) || string.IsNullOrEmpty(name) select c).ToList(); }

Consume the API method:

List<CustomerModel> customers = new List<CustomerModel>(); string apiUrl = "https://localhost:44318/api/CustomerAPI"; HttpClient client = new HttpClient(); HttpResponseMessage response = client.GetAsync(apiUrl + string.Format("/GetCustomers?name={0}", name)).Result; if (response.IsSuccessStatusCode) { customers = JsonConvert.DeserializeObject<List<CustomerModel>>(response.Content.ReadAsStringAsync().Result); }
lm1212 141 Reputation points

2022-05-24T03:20:48.063+00:00

Thanks for your help. I have tried a few different things and have not been able to get it to work. The MemoryStream system.io.read and write timeouts happen anyway from what I have read, so I can rule them out as being the problem. I tried using the JsonConvert.SerializeObject() method as suggested by Zhilv above (code below), but now I am getting the error "SerializationException: Expecting element 'root' from namespace ''.. Encountered 'None' with name '', namespace ''. " I am quite stuck on this, and would appreciate any more advice. Thank you.

var response2 = client.GetAsync(requestUri).Result;

if (response2.IsSuccessStatusCode) { var t = response2.Content.ReadAsStringAsync().Result; var d = JsonConvert.SerializeObject(t); var dcjs = new DataContractJsonSerializer(typeof(MovieSearch)); MemoryStream stream = new(); dcjs.WriteObject(stream, d); movieSearch = (MovieSearch)dcjs.ReadObject(stream); } return movieSearch;
Anonymous

2022-05-24T06:52:40.61+00:00

var t = response2.Content.ReadAsStringAsync().Result;

Try to set a break point to check the t value. What it looks like, a Json string or Html page?

var d = JsonConvert.SerializeObject(t);

After getting the response result, the t value should be a json string, then, we can use the JsonConvert.DeserializeObject() method to convert the json string to object, instead of the JsonConvert.SerializeObject method (this method is used to convert the an Object to a Json string).
lm1212 141 Reputation points

2022-05-24T08:28:24.9+00:00

var t = response2.Content.ReadAsStringAsync().Result;

If I click the down arrow next to the variable t in running (I use a breakpoint to stop the code there) all 3 options - Text, XML and HTML visualiser produce values, the text has a lot of data (starts with <!DOCTYPE html>), the XML value just reads " Upcoming Movies — The Movie Database (TMDB) " and the HTML value produces content we'd expect to find on a web page - links headings etc.. Basically the HTML rendered.

The other 1 option in the dropdown menu - JSON visualiser, produces the same value as the HTML page, except that it has a warning icon above the value container, which reads "String is not JSON formatted".

I wrote:

var d = JsonConvert.SerializeObject(t);

All the line above does is add [JSON]: to line 0 positon 0 of the JSON visualizer (when inspecting after placing breakpoint, (d is the same as t except is has [JSON]: in front of <!DOCTYPE html> in the JSON visualizer). It does not help though as when I write:

var t = response2.Content.ReadAsStringAsync().Result; var e = JsonConvert.DeserializeObject<MovieSearch>(t);

I get the same error as before: "encountered unexpected "<".

So the issue appears to me that the DeserializeObject method is still getting HTML instead of JSON.

Is there code / method which takes the incoming HTML file and transfers it to JSON, so i can then deserialize it?
Anonymous

2022-05-25T09:23:49.19+00:00

Yes, when using the DeserializeObject method, it required a JSON string, instead of the html.

Since we don't know what's the HTML content looks like, so can't directly give a answer, but you can try to use Regex.Match or String method (such as find or Substring) to get the data from the HTML content and then generate the JSON string.

Besides, if you can modify the API method, you can change the return data from html format to a JSON format, this might be more easier.

Answer 1

For the second time, the error is due to your code trying to deserialize HTML. What's confusing, if I understand your response above, is you are expecting an HTML response but the code is expecting JSON. Also, the response must be returning a status 200 (Ok) and not a 4XX error message.

I'm guessing is the client is calling an HTML page and not a REST service endpoint. That's why you're receiving an HTML stream with a 200 (ok) status. Use the debugger to verify the URL is correct. Also, it looks like you might be using one HttpClient for three different services. Can you verify?

    "TmdbSettings": {  
      "BaseUrl": "https://www.themoviedb.org/",  
      "BaseImagePath": "https://image.tmdb.org/t/p",  
      "BaseYouTubePath": "//www.youtube.com/watch?v=",  
      "QueryOptions": {  
        "Language": "en-US",  
        "AppendToResponse": "videos,release_dates,credits",  
        "Page": "1"  
      }  
    }

If you read the HttpClient reference documentation the recommendation is one HttpClient for each service because the HttpClient by design is scoped to the application not the request. Use the HttpClient factory pattern to fetch the HttpClient(s) the controller needs (constructor injection).

Make HTTP requests using IHttpClientFactory in ASP.NET Core

If you have one REST service and therefore one HttpClient then configure the base URL in the startup configuration. Again, I recommend the HttpClient factory pattern.

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SerializationException: There was an error deserializing the object of type ...Encountered unexpected character '<'.

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