Question

I use property setters to validate the input in a C# class and throw Exceptions on invalid inputs. I also use Json.NET to deserialize a json to an object. The problem is that I don’t know where to catch the exceptions for invalid json values which are thrown by the setters.
The Exception are not thrown from JsonConvert.DeserializeObject method.

public class A{
    private string a;

    public string number{
        get {return a;}
        set {
            if (!Regex.IsMatch(value, "^\\d+$"))
                throw new Exception();
            a = value;
        }
    }
}

public class Main
{
    public static void main()
    {
         // The Exception cannot be caught here.
         A a = JsonConvert.DeserializeObject<A>("{number:'some thing'}");
    }    
}

Answer 1

You need to subscribe to errors while deserializing your object:

            JsonConvert.DeserializeObject<A>("{number:'some thing'}",
            new JsonSerializerSettings
            {
                Error = (sender, args) =>
                {
                    Console.WriteLine(args.ErrorContext.Error.Message);
                    args.ErrorContext.Handled = true;
                }
            });

If you remove args.ErrorContext.Handled = true statement, exception raised in your setter will be rethrown from JsonConvert.DeserializeObject method. It will be wrapped in JsonSerializationException (” Error setting value to ‘number’ “).