C# - increment number and keep zeros in front

Question

I need to make a 40 digit counter variable. It should begin as 0000000000000000000000000000000000000001
and increment to
0000000000000000000000000000000000000002

When I use the int class, it cuts off all the zeros. Problem is I need to increment the number and then convert it to a string, with the correct number of leading zeros. The total size should be 40 digits. So if I hit 50 for example, it should look like this:

0000000000000000000000000000000000000050

How can I do that and retain the zeros?

You'll be needing to use something more like [BigInteger](http://msdn.microsoft.com/en-us/library/system.numerics.biginteger.aspx) rather than `int`, otherwise the increment will fail in short order. — HABO, Jun 07 '12 at 15:58

score 38 · Accepted Answer · edited May 23 '17 at 12:17

38

Use the integer and format or pad the result when you convert to a string. Such as

int i = 1;
string s = i.ToString().PadLeft(40, '0');

See Jeppe Stig Nielson's answer for a formatting option that I can also never remember.

edited May 23 '17 at 12:17

Community

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answered Jun 07 '12 at 15:35

Anthony Pegram

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@RhysW, no, it simply pads to the length you specify with the character also specified. It will not exceed that length. For example, "123".PadLeft(2, '0') will simply return "123" – Anthony Pegram Jun 07 '12 at 15:39

score 20 · Answer 2 · answered Jun 07 '12 at 15:36

20

Try using

int myNumber = ...;
string output = myNumber.ToString("D40");

Of course, the int can never grow so huge as to fill out all those digit places (the greatest int having only 10 digits).

answered Jun 07 '12 at 15:36

Jeppe Stig Nielsen

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alfongad · Answer 3 · 2012-06-07T15:54:32.393

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Just convert your string to int, perform the addition or any other operations, then convert back to string with adequate number of leading 0's:

// 39 zero's + "1"
string initValue = new String('0', 39) + "1";

// convert to int and add 1
int newValue = Int32.Parse(initValue) + 1;

// convert back to string with leading zero's
string newValueString = newValue.ToString().PadLeft(40, '0');

edited Jun 07 '12 at 15:54

answered Jun 07 '12 at 15:47

alfongad

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score 2 · Answer 4 · answered Jun 07 '12 at 15:53

2

I had to do something similar the other day, but I only needed two zeros. I ended up with

string str = String.Format("{0:00}", myInt);

Not sure if it's fool proof but try

String.Format("{0:0000000000000000000000000000000000000000}", myInt)

answered Jun 07 '12 at 15:53

Sapiens

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score 0 · Answer 5 · answered Apr 14 '20 at 01:45

0

You can use this too..

int number = 1;
string tempNumber = $"{number:00}";

result:

answered Apr 14 '20 at 01:45

rio gunawan

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C# - increment number and keep zeros in front

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