C#•2y ago

❔ Why does the JsonSerializer.Deserialize return a nullable object

I found this following example in the docs about the deserializer:

WeatherForecast? weatherForecast = 
                JsonSerializer.Deserialize<WeatherForecast>(jsonString);

            Console.WriteLine($"Date: {weatherForecast?.Date}");
            Console.WriteLine($"TemperatureCelsius: {weatherForecast?.TemperatureCelsius}");
            Console.WriteLine($"Summary: {weatherForecast?.Summary}");

WeatherForecast? weatherForecast = 
                JsonSerializer.Deserialize<WeatherForecast>(jsonString);

            Console.WriteLine($"Date: {weatherForecast?.Date}");
            Console.WriteLine($"TemperatureCelsius: {weatherForecast?.TemperatureCelsius}");
            Console.WriteLine($"Summary: {weatherForecast?.Summary}");

based on the docs it looks like it would throw an exception if the json can't be deserialized. The type, for deserialization, in this case is WeatherForecase not WeatherForecast? . Why does it return nullable<..>? Is there a way to make it return the acutal instance or just throw an error? I want to avoid many (maybe unnecessary) null checks? Thx!

4 Replies

Jimmacle•2y ago

because you can deserialize the string null

ero•2y ago

yeah, the literal contents

null

null

is a valid json object so if the input contains only that, then the deserialized object will also be null

nobodyOP•2y ago

ah I see, makes sense - thank you guys

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

Gaming

Programming

❔ Why does the JsonSerializer.Deserialize return a nullable object