using System;

using System.Collections.Generic;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

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

        datamodel.Add("Day", "11");     

        datamodel.Add("Month", "10");

        datamodel.Add("Year", "2022");

        var searchRegexPattern = "{Year}/{Month}/{Day}.xls";

        var rx = new Regex(@"\{(?<name>.*?)\}");

        var result = rx.Replace(searchRegexPattern, new MatchEvaluator(match => {

            return datamodel[match.Groups["name"].Value];

        }));

        Console.WriteLine(result);

    }

}