System.Text.JSON doesn't deserialize what Newtonsoft does
The default behavior of the System.Text.Json deserializer is to match properties as case sensitive. You need to pass options telling it to match case insensitive:
using System.Text.Json;JsonSerializer.Deserialize<T>(json_data, new JsonSerializerOptions { PropertyNameCaseInsensitive = true});
For setting globally, in startup.cs set
services.AddControllers(options => { }).AddJsonOptions(options => { options.JsonSerializerOptions.PropertyNameCaseInsensitive = true; options.JsonSerializerOptions.Encoder = JavaScriptEncoder.Default; });
if (response.IsSuccessStatusCode){ var json = await response.Content.ReadAsStringAsync(); var options = new JsonSerializerOptions { WriteIndented = true, PropertyNameCaseInsensitive = true // this is the point }; var books = JsonSerializer.Deserialize<IEnumerable<Book>>(json, options);}