I have an API in ASP Core 3.0 and an MVC client application in ASP Core 2.2. In the client application, I use HttpClient to call API methods and ReadAsStringAsync() to read responses and it works fine in debug.

When I publish to IIS on a real server, JSON responses are not properly read using response.Content.ReadAsStringAsync(). A string is created but JSON is unreadable, probably wrongly encoded, so I'm not able to convert it to an object.

I checked the response with Fiddler and everything looks fine, header Content-Type: application/json; charset=utf-8 is present and JSON looks good. I don't know what kind of IIS specific behavior produces this. I tried on a local instance of IIS and didn't reproduce this issue.

I've tried using Newtonsoft.Json to encode API response content and also tried adding [Produces("application/json")] to the API controller, the problem is still there.

Here is an example of what an API method returns :

return Ok(new UserDto { Login = user.Login, IdAccountUser = user.IdAccountUser, Prenom = user.Prenom, Nom = user.Nom, Token = tokenString }); 

And this how I read the response

HttpResponseMessage response = await _apiHttpClient.Post("users/authentication", user); string logDetail = string.Empty; if (response?.Content != null) { if (response.IsSuccessStatusCode) { string json = null; try { json = await response.Content.ReadAsStringAsync(); // Deserialization fails here because of invalid JSON user = JsonConvert.DeserializeObject<UserDto>(json); bool authenticationSuccessful = await AuthenticateUser(user); if (authenticationSuccessful) return string.IsNullOrEmpty(model.ReturnUrl) ? await Index() : Redirect($"~{model.ReturnUrl}"); } catch (JsonReaderException ex) { _logger.LogError(ex, "Erreur de lecture du JSON : {0}", json); } } else logDetail = $"Code HTTP réponse: {response.StatusCode}"; } 

_apiHttpClient.Post() is a custom wrapper for HttpClient.PostAsync()

I have an API in ASP Core 3.0 and an MVC client application in ASP Core 2.2. In the client application, I use HttpClient to call API methods and ReadAsStringAsync() to read responses and it works fine in debug.

When I publish to IIS on a real server, JSON responses are not properly read using response.Content.ReadAsStringAsync(). A string is created but JSON is unreadable, probably wrongly encoded, so I'm not able to convert it to an object.

I checked the response with Fiddler and everything looks fine, header Content-Type: application/json; charset=utf-8 is present and JSON looks good. I don't know what kind of IIS specific behaviour produces this. I tried on a local instance of IIS and didn't reproduce this issue.

I've tried using Newtonsoft.Json to encode the API response content and also tried adding [Produces("application/json")] to the API controller, the problem is still there.

Here is an example of what an API method returns :

return Ok(new UserDto { Login = user.Login, IdAccountUser = user.IdAccountUser, Prenom = user.Prenom, Nom = user.Nom, Token = tokenString }); 

And this how I read the response

HttpResponseMessage response = await _apiHttpClient.Post("users/authentication", user); string logDetail = string.Empty; if (response?.Content != null) { if (response.IsSuccessStatusCode) { string json = null; try { json = await response.Content.ReadAsStringAsync(); // Deserialization fails here because of invalid JSON user = JsonConvert.DeserializeObject<UserDto>(json); bool authenticationSuccessful = await AuthenticateUser(user); if (authenticationSuccessful) return string.IsNullOrEmpty(model.ReturnUrl) ? await Index() : Redirect($"~{model.ReturnUrl}"); } catch (JsonReaderException ex) { _logger.LogError(ex, "Erreur de lecture du JSON : {0}", json); } } else logDetail = $"Code HTTP réponse: {response.StatusCode}"; } 

_apiHttpClient.Post() is a custom wrapper for HttpClient.PostAsync()

I have an API in ASP Core 3.0 and a MVC client application in ASP Core 2.2. In client application, I use HttpClient to call API methods and ReadAsStringAsync() to read responses and it works fine in debug.

When I publish to IIS on a real server, JSON responses are not properly read using response.Content.ReadAsStringAsync(). A string is created but JSON is unreadable, probably wrongly encoded, so I'm not able to convert it to an object.

I checked the response with Fiddler and everything looks fine, header Content-Type: application/json; charset=utf-8 is present and JSON looks good. I don't know what kind of IIS specific behaviour produces this. I tried on a local instance of IIS and didn't reproduce this issue.

I've tried using Newtonsoft.Json to encode API response content and also tried adding [Produces("application/json")] to API controller, problem is still there.

Here is an example of what an API method returns :

return Ok(new UserDto { Login = user.Login, IdAccountUser = user.IdAccountUser, Prenom = user.Prenom, Nom = user.Nom, Token = tokenString }); 

And this how I read the response

HttpResponseMessage response = await _apiHttpClient.Post("users/authentication", user); string logDetail = string.Empty; if (response?.Content != null) { if (response.IsSuccessStatusCode) { string json = null; try { json = await response.Content.ReadAsStringAsync(); // Deserialization fails here because of invalid JSON user = JsonConvert.DeserializeObject<UserDto>(json); bool authenticationSuccessful = await AuthenticateUser(user); if (authenticationSuccessful) return string.IsNullOrEmpty(model.ReturnUrl) ? await Index() : Redirect($"~{model.ReturnUrl}"); } catch (JsonReaderException ex) { _logger.LogError(ex, "Erreur de lecture du JSON : {0}", json); } } else logDetail = $"Code HTTP réponse: {response.StatusCode}"; } 

_apiHttpClient.Post() is a custom wrapper for HttpClient.PostAsync()

I have an API in ASP Core 3.0 and an MVC client application in ASP Core 2.2. In the client application, I use HttpClient to call API methods and ReadAsStringAsync() to read responses and it works fine in debug.

When I publish to IIS on a real server, JSON responses are not properly read using response.Content.ReadAsStringAsync(). A string is created but JSON is unreadable, probably wrongly encoded, so I'm not able to convert it to an object.

I checked the response with Fiddler and everything looks fine, header Content-Type: application/json; charset=utf-8 is present and JSON looks good. I don't know what kind of IIS specific behavior produces this. I tried on a local instance of IIS and didn't reproduce this issue.

I've tried using Newtonsoft.Json to encode API response content and also tried adding [Produces("application/json")] to the API controller, the problem is still there.

Here is an example of what an API method returns :

return Ok(new UserDto { Login = user.Login, IdAccountUser = user.IdAccountUser, Prenom = user.Prenom, Nom = user.Nom, Token = tokenString }); 

And this how I read the response

HttpResponseMessage response = await _apiHttpClient.Post("users/authentication", user); string logDetail = string.Empty; if (response?.Content != null) { if (response.IsSuccessStatusCode) { string json = null; try { json = await response.Content.ReadAsStringAsync(); // Deserialization fails here because of invalid JSON user = JsonConvert.DeserializeObject<UserDto>(json); bool authenticationSuccessful = await AuthenticateUser(user); if (authenticationSuccessful) return string.IsNullOrEmpty(model.ReturnUrl) ? await Index() : Redirect($"~{model.ReturnUrl}"); } catch (JsonReaderException ex) { _logger.LogError(ex, "Erreur de lecture du JSON : {0}", json); } } else logDetail = $"Code HTTP réponse: {response.StatusCode}"; } 

_apiHttpClient.Post() is a custom wrapper for HttpClient.PostAsync()