You can utilize regular expressions and the Regex class. Here's an example code snippet that demonstrates how to achieve the desired replacements:

using System;
using System.Text.RegularExpressions;

public class Program
{
    public static void Main()
    {
        string text = "Your text with tags goes here";

        // Replace multiple   tags and 
 tags with a blank space
        text = Regex.Replace(text, @"( |
)", " ");

        // Replace 
 to 
 tags with the  tag
        text = Regex.Replace(text, @"", "");

        // Replace 
, 
, and 
 tags with specific characters
        text = Regex.Replace(text, @"
|
", match =>
        {
            if (match.Value.Contains("ol"))
            {
                return "$";
            }
            else
            {
                return " | ";
            }
        });

        Console.WriteLine(text);
    }
}