CODEWITHSUNDEEP
c#doubleprecision
Rand Random
Rand Random

Reputation: 7440

Double ToString gives rounded result

Why does this simple Console App Output 100000000000000 instead of 99999999999999.99 or atleast 99999999999999.984 as the debugger is showing?

static void Main(string[] args)
{
    double bigNum = 99999999999999.99;
    Console.WriteLine(bigNum); //Console.WriteLine will internally ToString, but you can add what ever ToString() you want here the result will always be undesired
}

Console Output:

Nope

Debug Output:

For clarification:

Yes, I know of the value type decimal and its superiour precision over double, but I never heard of that ToString() of double could give wrong results.

Upvotes: 2

Views: 387

Answers (1)

Stefan
Stefan

Reputation: 17648

See: MSDN for the standard ToString conversion:

If format is null or an empty string, the return value is formatted with the general numeric format specifier ("G").

This will show you, that the defaulted number format specifier "G", will default to max 15 digits if possible: G-format specifier

As requested:

double bigNum = 99999999999999.99;

Console.WriteLine(bigNum);                 //default
//100000000000000
Console.WriteLine(bigNum.ToString("G"));   //explicit default
//100000000000000
Console.WriteLine(bigNum.ToString("G17")); //G17
//99999999999999.984

Upvotes: 2

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