~/The Greatest string.FormatWith() Extension Method Implementation In The World
06 Apr 2014
This is in fact the Greatest string.FormatWith() Extension Method Implementation In The World. I have taken it with me for a few projects now. I found it in Perth, probably thanks to my brother-in-code Rob Moore correction turns out credit is due to Matt Kocoj, and I brought it back along the breadth of our mighty continent. A ‘Journey to the West’, if you will. Less awesome implementations of FormatWith() are just simple inversions of string.Format():
public static string FormatWith(string s, params object[] args)
{
return string.Format(s, args);
}
which you can use thusly:
"This is {0} the {1} {2} in the {3}".FormatWith(
"not", "greatest", "string.FormatWith() implementation", "world")
Nice, but let’s be honest, pitiful. Feel the power of this implementation.
public static class StringExtensions
{
public static string FormatWith(this string format, params object[] args)
{
args = args ?? new object[0];
string result;
var numberedTemplateCount = (from object match in new Regex(@"\{\d{1,2}\}").Matches(format) select match.ToString()).Distinct().Count();
if (numberedTemplateCount != args.Length)
{
var argsDictionary = args[0].ToDictionary();
if (!argsDictionary.Any())
{
throw new InvalidOperationException("Please supply enough args for the numbered templates or use an anonymous object to identify the templates by name.");
}
result = argsDictionary.Aggregate(format, (current, o) => current.Replace("{" + o.Key + "}", (o.Value ?? string.Empty).ToString()));
}
else
{
result = string.Format(format, args);
}
if (result == format)
{
throw new InvalidOperationException("You cannot mix template types. Use numbered templates or named ones with an anonymous object.");
}
return result;
}
}
public static class ObjectExtensions
{
public static IDictionary<string, object> ToDictionary(this object o)
{
if (o == null) return new Dictionary<string, object>();
return TypeDescriptor
.GetProperties(o).Cast<PropertyDescriptor>()
.ToDictionary(x => x.Name, x => x.GetValue(o));
}
}
This can be used in the same way as before:
"This is {0} the {1} {2} in the {3}".FormatWith(
"definitely", "greatest", "string.FormatWith() implementation", "world, but why?")
Or it can go full super-saiyan:
"{who} is {what} who {action} with {target}!".FormatWith(new{
who = "Hero",
what = "he alone",
action = "vies",
target = "powers supreme"})
WARNING: Now this is probably not the most performant code. If you’re going to run this in a tight loop you may want to go with ye olde string.Format(). The other 99.99% of the time, go forth and be awesome.
Updates
- 2014-04-23:
ToDictionary()is now in it’s own extension class, the named template conversion is simpler, and the numbered template conversion just usesstring.Format.