using System;

using System.Text.RegularExpressions;

using System.Collections.Generic;

using System.Linq;

// see: https://stackoverflow.com/q/50070908/1016343

public class Program

{

    public static void Main()

    {

        var values = new Dictionary<string, string>();

        values.Add("Value1","1");values.Add("Value2","example2");

        var templates = new Dictionary<string, string>

        {

            { "Key1", "{Value1}" },

            { "Key2", "Constant with {Value2}" }

        };

        var ans = templates.ToDictionary(kv => kv.Key, kv => kv.Value.Expand(values));

        ans.Dump();

    }       

}

​

public static class ExpandExt

{

    static Regex varPattern = new Regex(@"{(?<var>\w+)}", RegexOptions.Compiled);

    public static string Expand(this string src, Dictionary<string, string> vals) => varPattern.Replace(src, m => vals.TryGetValue(m.Groups[1].Value, out var v) ? v : m.Value);

}

​