c# how to prevent double value truncation when converting to string

Question

Double x = 11.123456789123456;
string y = Convert.ToString(x);
//gives y=11.1234567891235
//y should be =11.123456789123456

From the above code how can I prevent the last digit(6) from being truncated

Answer 1

Use

string y = x.ToString("G17");

or

string y = x.ToString("R");

as written here :

By default, the return value only contains 15 digits of precision although a maximum of 17 digits is maintained internally. If the value of this instance has greater than 15 digits, ToString returns PositiveInfinitySymbol or NegativeInfinitySymbol instead of the expected number. If you require more precision, specify format with the "G17" format specification, which always returns 17 digits of precision, or "R", which returns 15 digits if the number can be represented with that precision or 17 digits if the number can only be represented with maximum precision.

Note that not all the numbers can be represented exactly...

11.123456789123458.ToString("G17") == "11.123456789123457"

Answer 2

double is only precise up to 15-16 digits, try using decimal type

See Msdn

Decimal

Answer 3

The reason this is happening is because Double occupies 8 bytes and has precision of 15-16 digits. Use Decimal instead

Decimal x = 11.123456789123456M;
string y = Convert.ToString(x);
//gives y=11.12345678912356

Refer this link , look for answer by cds333