Float to String Conversion

Question

I want to convert float value to string.

Below is the code which i am using for the conversion.

static void Main(string[] args)
        {
            string s =string.Format("{0:G}", value);                
            Console.Write(s);
            Console.ReadLine();
        }

and it outputs as 2.5

But my problem is i want to get the value as 2.50 because i want to compare it with original value later in my project.

so please suggest me if there are any ways to do it?

Why are you comparing numbers by their string representation and not their value? — Corak, Sep 27 '13 at 06:19
That is requirement in my project. I have to compare the string(which i read from a file) if they are converted back properly.@Corak — Nomesh Gajare, Sep 27 '13 at 06:23

score 10 · Accepted Answer · edited Sep 27 '13 at 06:46

10

You should be using {0:N2} to format to two decimal places.

string.Format("{0:N2}", 2.50)

For 3 decimal places:

string.Format("{0:N3}", 2.50)

And so on.

You can also store the value in a string this way without worrying about precision and then convert your value where you are testing for comparison as string:

string strDecimalVal = Convert.ToString( 2.5000001);

edited Sep 27 '13 at 06:46

Marco

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answered Sep 27 '13 at 06:18

Sadique

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This way is great. But if i give 2.500 it should also output as 2.500 – Nomesh Gajare Sep 27 '13 at 06:25
See my edit. I have already mentioned how you can keep increasing the decimal width - :) – Sadique Sep 27 '13 at 06:26
yes i got that, but if i give 2.50 i want the output to be same. Not 2.500 if i specify {0:N3} – Nomesh Gajare Sep 27 '13 at 06:29
Then in that case do not format just convert to string like this: `Convert.ToString( 2.5000001)` and store in your string variable – Sadique Sep 27 '13 at 06:31
@NomeshGajare as a float, `2.50` is exactly the same as `2.500` or `2.5`. If you want to difference them you should store them as string literals. Edit: See [@heinzi 's answer](http://stackoverflow.com/a/19044089/1192381). – J.A.I.L. Sep 27 '13 at 06:41
Heinzi's answer is correct but floating point comparisons are not guaranteed to work in all case for eg if its Nan.http://stackoverflow.com/questions/19027762/why-convert-toint321-0-0-00004-int321-0-0-00004 – Sadique Sep 27 '13 at 06:45

score 5 · Answer 2 · edited May 23 '17 at 10:29

because i want to compare it with original value later in my project.

...then you will need to store the number of decimal places the original value had. Once the value is a float, this information is lost. The float representations of 2.5, 2.50 and 2.500 are exactly the same.

So, basically, you have the following possibilities (in order of preference):

Don't do a string comparison between the old and the new value. Convert both values to float and then compare them (with a margin of error since floats are not precise).
Store the number of decimal places of the old value and then use myFloat.ToString("F" + numDecimals.ToString()) to convert it to a string.
Store the value as a string instead of a float. Obviously, you won't be able to do math on that value.

Alternatively, if you do not insist on using floats, decimals might suit your purpose: The do store the number of significant digits:

decimal x = Decimal.Parse("2.50", CultureInfo.InvariantCulture);
decimal y = Decimal.Parse("2.500", CultureInfo.InvariantCulture);

Console.WriteLine(x.ToString()); // prints 2.50
Console.WriteLine(y.ToString()); // prints 2.500

score 1 · Answer 3 · answered Sep 27 '13 at 06:25

Try this

Console.WriteLine("{0:F2}", 2.50);
Console.WriteLine("{0:0.00}", 2.50);
Console.WriteLine("{0:N2}", 2.50);

Version 1 and 2 are almost similar, but 3 is different. 3 will include number separators when number is large.

For example the following outputs 454,542.50

Console.WriteLine("{0:N2}", 454542.50);

Float to String Conversion

3 Answers3