using System;

using System.Collections;

using System.Collections.Generic;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        ReplaceMultipleWithIgnoreCaseText();

    }

    public static void ReplaceMultipleWithIgnoreCaseText()

    {

        const string template = "My name is @Name@ and I like to read about @SUBJECT@ on @website@, tag @subject@";  

        const string expected = "My name is Alex and I like to read about C# on stackoverflow.com, tag C#";

        var replaceParameters = new List<KeyValuePair<string, string>>

        {

            new KeyValuePair<string, string>("@name@","Alex"),

            new KeyValuePair<string, string>("@subject@","C#"),

            new KeyValuePair<string, string>("@website@","stackoverflow.com"),

        };

        var actual = ReplaceMultiple(template, replaceParameters);

        Console.WriteLine(template);

        Console.WriteLine(expected);

        Console.WriteLine(actual);

    }

​

    public static string ReplaceMultiple(

                  string template, 

                  IEnumerable<KeyValuePair<string, string>> replaceParameters)

    {

        var result = template;

        foreach(var replace in replaceParameters)

        {

            var templateSplit = Regex.Split(result, 

                                            replace.Key, 

                                            RegexOptions.IgnoreCase);

            result = string.Join(replace.Value, templateSplit);

        }

        return result;

    }

}