Multi tool use

Json.NET decimal precision loss

I have an issue with deserializing decimal value.

JObject.Parse("{"available":8777.831438322572000}")


If I type this code in VS under debugger the result is

"available": 8777.8314383225716


If I try this

obj.Value<decimal>("available")


the result is 8777.83143832257

8777.83143832257

Where am I wrong?
What api methods should I use to get correct results?

2 Answers
2

The result of JObject.Parse("{"available":8777.831438322572000}") is a double. The second statement results in a decimal.

JObject.Parse("{"available":8777.831438322572000}")

double

decimal

The double has floating point precision, which is not that precise as a decimal.

double

decimal

Required reading: Why Floating-Point Numbers May Lose Precision

I find out that this problem doesn't relate to methods which take destination type as an argument. In case of untyped version method there is a setting which allows to change how json.net treats string with decimal separator. JsonReader.FloatParseHandling default value is FloatParseHandling.Double
In my case the way to get correct results is:

JsonReader.FloatParseHandling

FloatParseHandling.Double

JObject.Load(new JsonTextReader(new StringReader(value)) { FloatParseHandling = FloatParseHandling.Decimal }, null)


JsonSerializer and JsonSerializerSettings contain the same setting.

JsonSerializer

JsonSerializerSettings

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