using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;
using System.Reflection;

public class Test
{
	public static void Main()
	{
		string formatString = "{firstName} {lastName} is awesome at age {age}.";
		
		Console.WriteLine(formatString.FormatUnicorn(new {
			firstName = "joe",
			lastName = "blow",
			age = 13
		}));
	}
}

public static class StringExtensions {
	public static string FormatUnicorn(this string str, object arguments) {
		string output = str;

        Type type = arguments.GetType();

        foreach (PropertyInfo property in type.GetProperties())
        {
            Regex regex = new Regex(@"\{" + property.Name + @"\}");
            output = regex.Replace(output, property.GetValue(arguments, null).ToString());
        }

        return output;
	}
}