How do I add "123" to the beginning of a string and pad it to be exactly 12 chars?

Question

I need to add "123" and zeros for any string - but the resulting string must be exactly 12 characters long.

For example:

28431 = 123000028431
987   = 123000000987
2     = 123000000002

How to do this in C#?

Answer 1

Well, you could use:

string result = "123" + text.PadLeft(9, '0');

In other words, split the task in half - one part generating the "000028431", "000000987" etc part using string.PadLeft, and the other prefixing the result with "123" using simple string concatenation.

There are no doubt more efficient approaches, but this is what I'd do unless I had a good reason to believe that efficiency was really important for this task.

Answer 2

var result = string.Format("123{0}", number.PadLeft(9, '0'));