C#’s string interpolation supports alignment and format options

Alignment

Using the following syntax, {expression, alignment}, we can use negative alignment numbers for left-aligned expressions and positive numbers for right-aligned alignment. For example

var number = 123;
Console.WriteLine($"|{number,-10}|");
Console.WriteLine($"|{number,10}|");

This would produce the following

|123       |
|       123|

See also Alignment component.

Format String

We can use the following {expression, alignment:format} or {expression:format} syntax to add formatting, i.e.

var number = 123;
Console.WriteLine($"|{number, -10:F3}|");
Console.WriteLine($"|{number, 10:F3}|");

would produce the following

|123.000   |
|   123.000|

and

var number = 123;
Console.WriteLine($"|{number:F3}|");
Console.WriteLine($"|{number:F3}|");

would produce

|123.000|
|123.000|

See also Format string component.