Add zero-padding to a string

myInt.ToString("D4");

string strvalue="11".PadRight(4, '0');

output= 1100

string strvalue="301".PadRight(4, '0');

output= 3010

string strvalue="11".PadLeft(4, '0');

output= 0011

string strvalue="301".PadLeft(4, '0');

output= 0301

You can use PadLeft

var newString = Your_String.PadLeft(4, '0');