Padding a zero to the beginning of a string

Question

I have written a funny looking code that if the first character of string is blank, it will replace that blank space with a "0" and it works but like I said it is funny looking. Is there a nicer way of writing the same thing?

    char ch = value[0];
    if (ch == ' ')
    {
        value = value.Trim();
        value = "0" + value;
    }
    return value;

See [What's the best string concatenation method using C#?](http://stackoverflow.com/questions/21078/whats-the-best-string-concatenation-method-using-c). — CodeCaster, Nov 18 '13 at 13:23

score 8 · Accepted Answer · answered Nov 18 '13 at 13:30

8

It's as simple as:

if (value.Length > 0 && value[0] == ' ')
    value = '0' + value.Substring(1);

answered Nov 18 '13 at 13:30

Matthew Watson

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Actually, I'm not checking `value` for nullness - the OP didn't either, but if that's important then add a `value != null &&` to the `if` – Matthew Watson Nov 18 '13 at 13:41

score 1 · Answer 2 · answered Nov 18 '13 at 13:26

1

Whatever you want to achieve, this one is shorter:

if(value.StartsWith(" "))
{
  value = string.Format("0{0}", value.Trim());
}

answered Nov 18 '13 at 13:26

MatthiasG

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Almost. Will erroneously convert `__foo_` to `0foo` instead of `0_foo_`. – Rotem Nov 18 '13 at 13:33
I just converted the code of DevWannaBe, not the problem explained. It was difficult to know what was the intension of the question. – MatthiasG Nov 18 '13 at 13:37
1

you're right, the description doesn't match the OP's sample code. I just thought the caveat is worth mentioning. – Rotem Nov 18 '13 at 13:42

score 1 · Answer 3 · answered Nov 18 '13 at 13:28

1

if (value.StartsWith(" "))
{
    value = value.TrimStart(' ');
    value = value.PadLeft(value.Length + 1, '0');
}

Assuming value is not a null reference. For more information see this.

answered Nov 18 '13 at 13:28

Ondrej Tucny

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Guffa · Answer 4 · 2013-11-18T13:37:30.617

You can use a regular expression to match the spaces at the beginning of the string and replace with a zero character:

value = Regex.Replace(value, "^ +", "0");

If you only want to replace a single space at the beginning of the string, if there happen to be more than one:

value = Regex.Replace(value, "^ ", "0");

Note: This differs from your original implementation in two ways: It will only remove actual spaces from the beginning of the string, not any white space characters as the Trim method does, and it will only remove spaces from the beginning of the string, not also the end of the string, as the Trim method does. I assume that those details were not actually the intention of the code.

score 1 · Answer 5 · answered Nov 18 '13 at 13:39

I would use Trim() and PadLeft():

        string value = " 5678";
        value = value.Trim().PadLeft(5, '0');

If you had "1", or " 1", or any combination of "1" and spaces, it would end up being "00001".

You just change the 5 to however wide you need your field to be.

score 0 · Answer 6 · answered Nov 18 '13 at 13:30

0

Try this

 string value = " String with space";
 var firstChar = (byte)value.First();
 if (firstChar == ' ')
 {
    var regex = new Regex(Regex.Escape(" "));
    value = regex.Replace(value, "0", 1);
 }
 return value;

answered Nov 18 '13 at 13:30

Microsoft DN

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Is this really better than the original code? Maybe more complex or sophisticated, but better? – gehho Nov 18 '13 at 13:33

Padding a zero to the beginning of a string

6 Answers6