Variable String.Format length

Question

I have the following code:

var str = "ABC";
var n = 7;
var output = String.Format("{0,n}", str);

This should output the string

"    ABC"

How should I change the line above?

Answer 1

Format strings are just strings too - you can define the format separately:

int n = 3;
string format = string.Format("{{0,{0}}}", n);
//or more readable: string format = "{0," + n + "}";
var output = string.Format(format, str);

Edit:

After your update it looks like what you want can also be achieved by PadLeft() :

var str = "ABC";
string output = str.PadLeft(7);

Answer 2

写吧：

var lineLength = String.Format("{0," + n + "}", str);

Answer 3

var s="Hello my friend";
string leftSpace = s.PadLeft(20,' '); //pad left with special character
string rightSpace = s.PadRight(20,' '); //pad right with special character