URL-encoded slash in URL

My Map is:

routes.MapRoute(
   "Default",                                             // Route name
   "{controller}/{action}/{id}",                          // URL with params
   new { controller = "Home", action = "Index", id = "" } // Param defaults
);

If I use the URL http://localhost:5000/Home/About/100%2f200 there is no matching route. I change the URL to http://localhost:5000/Home/About/100 then the route is matched again.

Is there any easy way to work with parameters that contain slashes? Other escaped values (space %20) seem to work.

EDIT:

To encode Base64 works for me. It makes the URL ugly, but that's OK for now.

public class UrlEncoder
{ 
    public string URLDecode(string  decode)
    {
        if (decode == null) return null;
        if (decode.StartsWith("="))
        {
            return FromBase64(decode.TrimStart('='));
        }
        else
        {
            return HttpUtility.UrlDecode( decode) ;
        }
    }

    public string UrlEncode(string encode)
    {
        if (encode == null) return null;
        string encoded = HttpUtility.PathEncode(encode);
        if (encoded.Replace("%20", "") == encode.Replace(" ", ""))
        {
            return encoded;
        }
        else
        {
            return "=" + ToBase64(encode);
        }
    }

    public string ToBase64(string encode)
    {
        Byte[] btByteArray = null;
        UTF8Encoding encoding = new UTF8Encoding();
        btByteArray = encoding.GetBytes(encode);
        string sResult = System.Convert.ToBase64String(btByteArray, 0, btByteArray.Length);
        sResult = sResult.Replace("+", "-").Replace("/", "_");
        return sResult;
    }

    public string FromBase64(string decode)
    {
        decode = decode.Replace("-", "+").Replace("_", "/");
        UTF8Encoding encoding = new UTF8Encoding();
        return encoding.GetString(Convert.FromBase64String(decode));
    }
}

EDIT1:

At the end it turned out that the best way was to save a nicely formated string for each item I need to select. Thats much better because now I only encode values and never decode them. All special characters become "-". A lot of my db-tables now have this additional column "URL". The data is pretty stable, thats why I can go this way. I can even check, if the data in "URL" is unique.

EDIT2:

Also watch out for space character. It looks ok on VS integrated webserver but is different on iis7 Properly url encode space character

If it's only your last parameter, you could do:

routes.MapRoute(
    "Default",                                                // Route name
    "{controller}/{action}/{*id}",                            // URL with parameters
    new { controller = "Home", action = "Index", id = "" });  // Parameter defaults

Here's a simple explanation of the solution and a summation of what has already been said.

Request side:

1. UrlEncode your path.
2. Replace the '%' with '!'.
3. Make the request.

Response side:

1. Replace the '!' with '%'.
2. UrlDecode your path.
3. Use the parameters as they were intended.

Rinse, repeat, enjoy.

In .NET 4.0 beta 2, the CLR team has offered a workaround.

Add this to your web.config file:

<uri> 
    <schemeSettings>
        <add name="http" genericUriParserOptions="DontUnescapePathDotsAndSlashes" />
    </schemeSettings>
</uri>

This causes the Uri class to behave according to the RFC describing URIs, allowing for slashes to be escaped in the path without being unescaped. The CLR team reports they deviate from the spec for security reasons, and setting this in your .config file basically makes you take ownership of the additional security considerations involved in not unescaping the slashes.