JsonSerializer - serialize decimal places with 'N2' formatting - asp.net-mvc

Question

I'm serializing decimals using Newtonsoft.Json.JsonSerializer.
How can I set it to serialize decimal numbers with only 1 decimal place to use 0 at the end.
i.e. 3.5 serializes to "3.50"?

Answer 1

You'll have to write your own custom JsonConverter and use it to intercept the decimal type so you can change how it gets serialized. Here's an example:
public class DecimalFormatConverter : JsonConverter
{
public override bool CanConvert(Type objectType)
{
return (objectType == typeof(decimal));
}
public override void WriteJson(JsonWriter writer, object value,
JsonSerializer serializer)
{
writer.WriteValue(string.Format("{0:N2}", value));
}
public override bool CanRead
{
get { return false; }
}
public override object ReadJson(JsonReader reader, Type objectType,
object existingValue, JsonSerializer serializer)
{
throw new NotImplementedException();
}
}
To use it, simply pass in a new instance of this custom converter to the SerializeObject method:
var json = JsonConvert.SerializeObject(yourObject, new DecimalFormatConverter());

Answer 2

The accepted answer is correct, but expanding upon the comments on accepted answer:
If you want the decimals in your JSON to be numbers instead of strings, you need to use WriteRawValue and use :0.00 instead of :N2 for the string formatting (as N2 includes thousand separator commas and other culture specific number formatting that will break your JSON)
public class DecimalFormatConverter : JsonConverter
{
public override bool CanConvert(Type objectType)
{
return objectType == typeof(decimal);
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
writer.WriteRawValue($"{value:0.00}");
}
public override bool CanRead => false;
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
throw new NotImplementedException();
}
}
This is the difference in output compared to the accepted answer.
# writer.WriteRawValue($"{value:0.00}");
{
"MyDecimal": 3.50,
"MyBiggerDecimal": 12345.50
}
# writer.WriteValue($"{value:N2}");
{
"MyDecimal": "3.50",
"MyBiggerDecimal": "12,345.50"
}
Note - the accepted answer is correct for the OP's specific question i.e. serialize 3.5 to "3.50", but I got here wanting to serialize 3.5 to 3.50 (without the string quotes).

Answer 3

Hy!
The second answer is also correct, but not reflecting Cultures.
If you want to have really 0.00 (with .) you have to use:
public class DecimalFormatConverter : JsonConverter
{
public override bool CanConvert(Type objectType)
{
return objectType == typeof(decimal);
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
FormattableString formattableString = $"{value:0.00}";
writer.WriteRawValue(formattableString.ToString(CultureInfo.InvariantCulture));
}
public override bool CanRead => false;
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
throw new NotImplementedException();
}
}
With this it is garantueed to have dot as decimal separater.
The difference is:
FormattableString formattableString = $"{value:0.00}";
writer.WriteRawValue(formattableString.ToString(CultureInfo.InvariantCulture));