using System;

using System.Collections.Generic;

using System.Text.RegularExpressions;

​

public class Program

{

    public static void Main(string[] args)

    {

        string input = "{entry1} {entry2} this is a string";

        Dictionary<string, string> dictionary = new Dictionary<string, string> { { "entry1", "foo" }, { "entry2", "bar" } };

​

        var result = dictionary.ReplaceKeyInString(input);

        Console.WriteLine(result);

    }

}

​

public static class DictionaryExtensions

{

    public static string ReplaceKeyInString(this Dictionary<string, string> dictionary, string inputString)

    {

        var regex = new Regex("{(.*?)}");

        var matches = regex.Matches(inputString);

        foreach (Match match in matches)

        {

            var valueWithoutBrackets = match.Groups[1].Value;

            var valueWithBrackets = match.Value;

​

            if(dictionary.ContainsKey(valueWithoutBrackets))

                inputString = inputString.Replace(valueWithBrackets, dictionary[valueWithoutBrackets]);

        }

​

        return inputString;

    }

}