C# Pulled Json Double-Values addition anomaly?

Question

As described in the title im pulling a ton of values from a json string, replacing the "." with ",", converting them to double and adding them up. The anomaly here seems to be that while the string only contains numbers with 2 digits, the endresult ends with .x9999999x! If you have any fix or explanation, it is appreciated.

Much smaller JSON Example:

{"AK-47 | Aquamarine Revenge (Factory New)":"33.74","AK-47 | Aquamarine Revenge (Minimal Wear)":"23.35",
"AK-47 | Aquamarine Revenge (Field-Tested)":"17","AK-47 | Aquamarine Revenge (Well-Worn)":"14.5","AK-47 | Aquamarine Revenge (Battle-Scarred)":"11.7",
"StatTrak™ AK-47 | Aquamarine Revenge (Factory New)":"123.16","StatTrak™ AK-47 | Aquamarine Revenge (Minimal Wear)":"75.84","StatTrak™ AK-47 | Aquamarine Revenge (Field-Tested)":"54.2",
"StatTrak™ AK-47 | Aquamarine Revenge (Well-Worn)":"38.33","StatTrak™ AK-47 | Aquamarine Revenge (Battle-Scarred)":"31.24","AK-47 | Black Laminate (Factory New)":"91.3",
"AK-47 | Black Laminate (Minimal Wear)":"9.86","AK-47 | Black Laminate (Field-Tested)":"8.11","AK-47 | Black Laminate (Well-Worn)":"9","AK-47 | Black Laminate (Battle-Scarred)":"9.3",
"AK-47 | Bloodsport (Factory New)":"63.55","AK-47 | Bloodsport (Minimal Wear)":"55.7","AK-47 | Bloodsport (Field-Tested)":"49.35","AK-47 | Bloodsport (Well-Worn)":"48.31",
"StatTrak™ AK-47 | Bloodsport (Factory New)":"222.89","StatTrak™ AK-47 | Bloodsport (Minimal Wear)":"182.08"}

Added value example:

61241,69999998

EDIT:

I changed all calculations from Conver.ToDouble() to Convert.ToDecimal and now it seems to be fixed. Can anyone explain why the other one wasn't working although there are only 2-digit numbers??

Answer 1

You must be deserializing to floating point numbers. If so the string "61241,70" may well be converted to the 61241,69999998 float value. Change your float variables to decimal .

This happens because float (and other floating-point types) store values in digital binary format, which cannot represent/store certain decimal values exactly given their limited precision. On the other hand, decimal type stores decimal values exactly.

A very good explanation is here . The issue is also discussed here , specifically in the point 2 of the accepted answer