Question

Can anyone help me how to optimize this method?

public override VirtualPathData GetVirtualPath(RequestContext requestContext, RouteValueDictionary values)
{
    VirtualPathData path = base.GetVirtualPath(requestContext, values);

    if (path != null)
    {
        string virtualPath = path.VirtualPath;
        string condition = string.Empty;

        if (virtualPath.Contains("?"))
        {
            condition = virtualPath.Substring(virtualPath.IndexOf("?"));
            virtualPath = virtualPath.Substring(0, virtualPath.IndexOf("?"));
        }

        virtualPath = virtualPath.Replace(@"%C5%BD", "ž");
        virtualPath = virtualPath.Replace(@"%C4%90", "đ");
        virtualPath = virtualPath.Replace(@"%C4%86", "ć");
        virtualPath = virtualPath.Replace(@"%C4%8C", "č");
        virtualPath = virtualPath.Replace(@"%C5%A0", "š");

        virtualPath = virtualPath.ToLower().Replace(",", "-").Replace("%20", "-").Replace("&", "-");
        virtualPath = virtualPath.Replace(@"-amp;", "&");

        while (virtualPath.Contains("--"))
        {
            virtualPath = virtualPath.Replace("--", "-");
        }

        path.VirtualPath = virtualPath + condition;
    }

    return path;
}

Answer 1

In this code you are scanning the string three times for a character:

if (virtualPath.Contains("?"))
{
   condition = virtualPath.Substring(virtualPath.IndexOf("?"));
   virtualPath = virtualPath.Substring(0, virtualPath.IndexOf("?"));
}

Instead, scan it once and use the result three times. Also scan for a char instead of a string:

int pos = virtualPath.IndexOf('?');
if (pos != -1) {
   condition = virtualPath.Substring(pos);
   virtualPath = virtualPath.Substring(0, pos);
}

---

Here you are doing several replaces with the same replacement:

virtualPath = virtualPath.ToLower().Replace(",", "-").Replace("%20", "-").Replace("&", "-");

Instead you can use a regular expression to match all of them:

virtualPath = Regex.Replace(virtualPath.ToLower(), "(,|%20|&)", "-");

(Whether this actually gives better performance has to be tested with some of your actual data. Eventhough it’s less operations, there is some overhead in setting up the regular expresson.)

---

You are using a loop to reduce clusters of characters:

while (virtualPath.Contains("--"))
{
   virtualPath = virtualPath.Replace("--", "-");
}

Instead you can use a regular expression to make a single replacement:

virtualPath = Regex.Replace(virtualPath, "-{2,}", "-");