Problem with Padleft

Question

I have a problem using the Padleft method. I need to put some zeros in front of a string, but I’m not getting it. For example:

string value = "2001795";
string newValue = value.PadLeft(5, '0');

Theoretically, the string "newValue" should have the value "000002001795", right? But this is not working...

Answer 1

Theoretically, the string "newValue" should have the value "000002001795", right?

No. The PadLeft serves to complete a string with any character, which is passed as the second parameter of the method, until it reaches the number of characters entered in the first parameter.

For example:

var value = "123";
var newValue = value.PadLeft(5, '0');

// Saída 00123

If you only need to put 5 zeros in front of the string, you only need to concatenate.

var value = "123";
var newValue = "00000" + value;

// Saída 00000123

Answer 2

The method PadLeft, adds characters to the left until you complete your string complete the number of characters reported, if the string already have at least this amount of characters nothing will happen.

In your case, it will add 0 to the left until your string complete 5 characters, as your variable has 7 characters, nothing will happen. If you replace for example with:

string value = "2001795";
string newValue = value.PadLeft(10, '0');

The value of newValue would be 0002001795, because he would add 3 0 left until he completed 10 characters.

Answer 3

The first argument is the maximum amount (totalWidth) that the string should have. You said the maximum size is 5, 2001795 has more than 5 characters, so you didn’t have to complete.

Correct form:

 string newValue = value.PadLeft(12,'0');

https://msdn.microsoft.com/pt-br/library/system.string.padleft(v=vs.110). aspx