How could I convert data from string to long in c#

Question

How could i convert data from string to long in C#?

I have data

String strValue[i] ="1100.25";

now i want it in

long l1;

Longs represent integers. You've given a non-integer. What would you want to do with that? — Jon Skeet, Jun 13 '11 at 12:21
What if strValue is "1100.75" ? See: http://stackoverflow.com/questions/633335/how-might-i-convert-a-double-to-the-nearest-integer-value — magma, Jun 13 '11 at 12:22
@magma: if you convert it into decimal then it will round off the number, i.e in this case if given number was 1100.75 then it will output 1101. — love Computer science, Jun 13 '11 at 12:47
@charlie I was merely raising the issue, because MayP did not appear to be fully aware of the implication here. He might want to simply get rid of the non-integer part without any rounding, and that's fine, provided that it's really what he wants. Thank you though. — magma, Jun 13 '11 at 13:19

BrunoLM · Answer 1 · 2011-06-13T12:26:12.357

64

If you want to get the integer part of that number you must first convert it to a floating number then cast to long.

long l1 = (long)Convert.ToDouble("1100.25");

You can use Math class to round up the number as you like, or just truncate...

edited Jun 13 '11 at 12:26

answered Jun 13 '11 at 12:20

BrunoLM

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This is going to give you `FormatException` if you run this on the specified input. – Andrew Savinykh Jun 13 '11 at 12:22
1

@zespri, no, at least not in most cultures... But it would indeed fail in cultures where the decimal separator is not "." – Thomas Levesque Jun 13 '11 at 12:23
using your code, this value 2037104000005652013 changed to 2037104000005651968. ? – Pranesh Janarthanan Sep 24 '20 at 07:26
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You need to specify an explicit culture that treats `.` as a decimal separator (`CultureInfo.InvariantCulture` would work). – Etienne de Martel Feb 16 '22 at 16:33
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@PraneshJanarthanan The biggest integer that can be safely represented in a `double` is `2^53`, and yours is bigger than that, so when converted to a long you'll get some funky results. – Etienne de Martel Feb 16 '22 at 16:36

score 53 · Answer 2 · answered Aug 08 '18 at 06:05

53

You can also use long.TryParse and long.Parse.

long l1;
l1 = long.Parse("1100.25");
//or
long.TryParse("1100.25", out l1);

answered Aug 08 '18 at 06:05

majid zareei

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score 21 · Answer 3 · answered Jun 13 '11 at 12:22

21

http://msdn.microsoft.com/en-us/library/system.convert.aspx

l1 = Convert.ToInt64(strValue)

Though the example you gave isn't an integer, so I'm not sure why you want it as a long.

answered Jun 13 '11 at 12:22

John

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score 13 · Answer 4 · edited Jul 13 '20 at 10:07

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long l1 = Convert.ToInt64(strValue);

That should do it.

edited Jul 13 '20 at 10:07

Pang

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answered Jun 13 '11 at 12:22

stuartmclark

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Not recomended when used with linq. It gives me an exception. long.Parse("1100.25") works for me – César León May 03 '22 at 23:16

score 7 · Answer 5 · answered Jun 13 '11 at 12:41

You won't be able to convert it directly to long because of the decimal point i think you should convert it into decimal and then convert it into long something like this:

String strValue[i] = "1100.25";
long l1 = Convert.ToInt64(Convert.ToDecimal(strValue));

hope this helps!

score 3 · Answer 6 · edited Jun 16 '14 at 22:15

3

long is internally represented as System.Int64 which is a 64-bit signed integer. The value you have taken "1100.25" is actually decimal and not integer hence it can not be converted to long.

You can use:

String strValue = "1100.25";
decimal lValue = Convert.ToDecimal(strValue);

to convert it to decimal value

edited Jun 16 '14 at 22:15

BenMorel

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answered Jun 13 '11 at 12:31

sandyiit

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score 1 · Answer 7 · answered Jun 13 '11 at 12:29

1

You can also do using Int64.TryParse Method. It will return '0' if their is any string value but did not generate an error.

Int64 l1;

Int64.TryParse(strValue, out l1);

answered Jun 13 '11 at 12:29

Pankaj Agarwal

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Cosmin Sontu · Answer 8 · 2020-07-23T20:44:02.483

You can create your own conversion function:

    static long ToLong(string lNumber)
    {
        if (string.IsNullOrEmpty(lNumber))
            throw new Exception("Not a number!");
        char[] chars = lNumber.ToCharArray();
        long result = 0;
        bool isNegative = lNumber[0] == '-';
        if (isNegative && lNumber.Length == 1)
            throw new Exception("- Is not a number!");

        for (int i = (isNegative ? 1:0); i < lNumber.Length; i++)
        {
            if (!Char.IsDigit(chars[i]))
            {
                if (chars[i] == '.' && i < lNumber.Length - 1 && Char.IsDigit(chars[i+1]))
                {
                    var firstDigit = chars[i + 1] - 48;
                    return (isNegative ? -1L:1L) * (result + ((firstDigit < 5) ? 0L : 1L));    
                }
                throw new InvalidCastException($" {lNumber} is not a valid number!");
            }
            result = result * 10 + ((long)chars[i] - 48L);
        }
        return (isNegative ? -1L:1L) * result;
    }

It can be improved further:

performance wise
make the validation stricter in the sense that it currently doesn't care if characters after first decimal aren't digits
specify rounding behavior as parameter for conversion function. it currently does rounding

How could I convert data from string to long in c#

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