Regex validation for relative paths

I got it to work with the one dot instead below.

".\\Input\\Example.xml"

I had to specify the directory below like this to get it to work.

"..\\Temp\\Input\\Example.xml"

Well, if the current directory is the one which contains example.exe, then:

  "\input\example.txt"

won't exist.

You'll either have to use:

  "input\example.txt"

or:

 ".\input\example.txt"   // note, just one dot

as I said in my previous post.

I want to account for every situation possible.

But for some reason. I am getting the directory do not exist.
When I set the string to "\input\example.txt"

I'm not understanding why it keep jumping into the case the directory does not exist. If you view the screen shot it does exist.

 FileInfo fileInfo = new FileInfo(fileName);

 //Verify if directory exists on local disks.
 if (!Directory.Exists(fileInfo.DirectoryName))
 {
        throw new ArgumentNullException("fileInfo.DirectoryName", "Specified directory                    does not exist. Please specify a existing directory.");
 }

The relative path would be either:

input\example.xml

or

.\input\example.xml

It would be easy to allow for the second one but major surgery would be needed to allow for the first one.

Are you wanting here a regular expression that deals with relative paths in isolation or one that can deal with both absolute and relative paths?

Also are you wanting to allow for the possible use of  '/' rather than '\' which is another awkward point to deal with?

If you can clarify, I'll have another think about it tomorrow as it's past midnight here now.

Review image below. What will be the relative from the Example.exe in the image attachment.
I am still getting an error. Try this out below.

string regExp = @"^(?:[A-Za-z]\:|\\\.\.|\.\.|\\)(\\|\\[a-zA-Z_\-\s0-9\.]+)+(\.\w+)?$";

Regex r= new Regex(regExp);
                if (!r.IsMatch("//Input//test.xml))
                {
                    throw new ArgumentNullException("fileName", "A valid filepath/filename is required. Please specify a valid filepath/filename.");
                }

Try this one instead:

string regExp = @"^(?:[A-Za-z]\:|\\\.\.|\.\.|\\)(\\|\\[a-zA-Z_\-\s0-9\.]+)+(\.\w+)?$";

Vuples I have a question.

What if a user type Backslash Backslash first before the two dots below.


At the moment this does not work:

"\\..\\..\\Bin\\Test.xml"


This works:

"..\\..\\Bin\\Example.xml"

Try:

 string regExp = @"^(?:[A-Za-z]\:|\\|\.\.)(\\[a-zA-Z_\-\s0-9\.]+)+(\.\w+)?$";