在C＃中生成固定长度的字符串

Question

如何根据c＃中给出的输入生成一个固定长度的字符串。

For example :
string s="1";
string newstring ;
I want the newstring to be "AB_000001";
// Similarly if 
s="xyz";
//I want the newstring as 
newstring = "AB_000xyz";

Answer 1

string basestr = "AB_000000";
string inp = "xyz";
string res = basestr.Substring(0, basestr.Length - inp.Length) + inp;

Answer 2

String s = "AB_000000";
String newString="xyz";
s = s.Remove(s.Length - newString.Length, newString.Length);
s = s + newString;