Question

The following code does not work all the time. I have looked at countless regex examples but very few address the use of multiple extensions.

public bool FAQPNFileCheck(string name)
{
    if (name.Length > 0)
    {

        Match match = Regex.Match(name, 
                                  @"\\([A-Za-z0-9_-]+)\.(jpg|doc|pdf)$", 
                                  RegexOptions.IgnoreCase);

        // Here we check the Match instance.
        if (match.Success)
        {
            // Finally, we get the Group value and display it.
            string key = match.Groups[1].Value;
            return true;
            //Console.WriteLine(key);
        }

    }
    if (name == "")
    {
        return true;
    }

    return false;
}

Answer 1

Ok, so after all, you want to allow files with the extesions jpg, doc or pdf, right?

Let’s try this:

Regex.Match(name, @"^(?i:[A-Z0-9\_\-]+)\.(?i:jpg|doc|pdf)$", RegexOptions.Compiled);

As latkin pointed out, if you’re going to use this Regex object once, then RegexOptions.Compiled is not a good choice, because it will take longer to instantiate the object. However, the match will run faster, so it’s a good idea to keep it if you’re going to use it on several files (as I was supposing), then keep it at a Regex instance.