Handling decimal values in Newtonsoft.Json

Question

Edit: It\'s been almost 5 years and I don\'t think this is the way to go. The client should post the data in the correct numerical format. With current fram

Answer 1

As an extension to Kwaazaar's answer, I have added the reverse way to the converter as well (In his example it throws a NotImplementedException.

namespace Something.Converter
{
    using System;

    using Newtonsoft.Json;
    using Newtonsoft.Json.Linq;

    /// 
    /// 

    /// Converts an object to and from JSON.
    /// 
    /// 
    public class DecimalConverter : JsonConverter
    {
        /// 

        /// Gets a new instance of the .
        /// 
        public static readonly DecimalConverter Instance = new DecimalConverter();

        /// 
        /// 

        /// Determines whether this instance can convert the specified object type.
        /// 
        /// Type of the object.
        /// 
        ///     true if this instance can convert the specified object type; otherwise, false.
        /// 
        /// 
        public override bool CanConvert(Type objectType)
        {
            return objectType == typeof(decimal) || objectType == typeof(decimal?);
        }

        /// 
        /// 

        /// Reads the JSON representation of the object.
        /// 
        /// The  to read from.
        /// Type of the object.
        /// The existing value of object being read.
        /// The calling serializer.
        /// The object value.
        /// 
        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
        {
            if (!(reader.Value is string value))
            {
                if (objectType == typeof(decimal?))
                {
                    return null;
                }

                return default(decimal);
            }

            // ReSharper disable once StyleCop.SA1126
            if (decimal.TryParse(value, out var result))
            {
                // ReSharper disable once StyleCop.SA1126
                return result;
            }

            if (objectType == typeof(decimal?))
            {
                return null;
            }

            return default(decimal);
        }

        /// 
        /// 

        /// Writes the JSON representation of the object.
        /// 
        /// The  to write to.
        /// The value.
        /// The calling serializer.
        /// 
        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        {
            var d = default(decimal?);

            if (value != null)
            {
                d = value as decimal?;
                if (d.HasValue)
                {
                    d = new decimal(decimal.ToDouble(d.Value));
                }
            }

            JToken.FromObject(d ?? 0).WriteTo(writer);
        }
    }
}

To plug this into your binder, just add an instance of the converter to the Converters list in the JsonSerializerSettings object:

JsonSerializerSettings settings = new JsonSerializerSettings
{
    // Some other settings.
    Converters = new List { new DecimalConverter() }
};

or

JsonSerializerSettings settings = new JsonSerializerSettings
{
    // Some other settings.
    Converters = new List { DecimalConverter.Instance }
};