using System;

using System.Collections.Generic;

using System.Text.RegularExpressions;

public class Program {

  private static string MyProcess(string text, IDictionary<string, string> replacements) => Regex.Replace(

        text ?? "",

        @"\{(?<name>.*?)\}",

        match => replacements.TryGetValue(match.Groups["name"].Value, out var value) ? value : "???");  

  public static void Main() {

    // All possible substitutions (from database?)

    Dictionary<string, string> replacements = 

      new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase) {

        { "name", "Frodo"},

        { "country", "Shire"},

    };

​

    // Text to process  

    string greet = "Hi {name}! Are you from {country}?";

​

    // No hardcoding, just process string - here is greeting

    // with respect from replacement  

    string result = MyProcess(greet, replacements);

    Console.WriteLine(result);  

  }

}