String Interpolation with format variable

Question

I can do this:

var log = string.Format(\"URL: {0}\", url);

or even like this

var format = \"URL: {0}\";
...
var log = strin         


        

Answer 1

String interpolation is a compiler, not library, feature.

The holes are not names, but expressions:

var r = new Rectangle(5, 4);
var s = $"area: {r.Width + r.Heigh}":

How would you do that for localization, as you intend to?

Even r only exists at compile time. In IL it's just a position on the method's variable stack.

I've done what you intend to do for resources and configuration files.

Since you can only have a finite set of "variables" to substitute, what I did was have an array (or dictionary, if you prefer) and use a regular expression to replace the names in the holes with its index. What I did even allowed for format specifiers.