Question 111096 in Json Question posted in
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Json – How to make ASP.NET Core bind partially to valid data?

Let’s say I have this model:

public enum State
{
    Valid = 1,
    Invalid = 2
}

public class Person
{
    public string Name { get; set; }
    
    public State state { get; set; }
}

And this controller action:

[HttpPost]
public object SavePerson([FromBody] Person person)
{
    return person;
}

If I send this JSON, everything works just fine:

{
    "name": "John",
    "state": 1
}

However, if I change the "state": 1 to an invalid enumeration like "state": "" or "state": "1", then the person parameter would be null.

In other words, if I send a JSON that is partially valid, ASP.NET Core ignores all fields.

How can I configure ASP.NET Core to at least extract the valid fields from the body?

Tags:

2

Answers


  1. 0

    You need to handle deserialization exception.

    This code will put a default value each time it will encounter a problem in a field but the json string itself must be a valid json string.

        static void Main(string[] args)
    {
        //This should be run on startup code (there are other ways to do that as well - you can put this settings only on controllers etc...)
        JsonConvert.DefaultSettings = () => new JsonSerializerSettings
        {
            Error = HandleDeserializationError
        };

        var jsonStr = "{"name": "John","state": "" }";
        var person = JsonConvert.DeserializeObject<Person>(jsonStr);         

        Console.WriteLine(JsonConvert.SerializeObject(person)); //{"Name":"John","state":0}
    }

    public static void HandleDeserializationError(object sender, ErrorEventArgs args)
    {
        var error = args.ErrorContext.Error.Message;
        args.ErrorContext.Handled = true;
    }

    For WebAPI you should have a Startup.cs file looks like this:

        public void ConfigureServices(IServiceCollection services)
    {
        //look for services.AddControllers() -> or add it if it does not exist
        services.AddControllers()
            .AddMvcOptions(options =>
            {
               //... might have options here
            })
               //this is what you need to add
            .AddNewtonsoftJson(options =>
            {
                options.SerializerSettings.Error = HandleDeserializationError
            });
    }
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  2. 0

    Try this nullable operator:

    public State? state { get; set; }
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